[EEM] Fix ingest pipeline to not overwrite existing parents in metadata (#186672)

## Summary

This fixes #186668 by adding a check to see if a `HashMap` exists before
creating a new one. This happens when the ingest pipeline converts the
output from a transfrom's `terms` sub-aggregation output to a list of
terms.

### Testing

Use Syntrace to generate data with this command:
```
node scripts/synthtrace packages/kbn-apm-synthtrace/src/scenarios/continuous_rollups.ts --live
```
Then create this Entity definition:
```JSON
POST kbn:/internal/api/entities/definition
{
  "id": "apm-countinuous-rollups",
  "name": "Services for APM",
  "type": "service",
  "indexPatterns": ["logs-*", "metrics-*", "traces-*"],
  "history": {
    "timestampField": "@timestamp",
    "interval": "1m"
  },
  "identityFields": ["service.name", "service.environment"],
  "displayNameTemplate": "{{service.name}}:{{service.environment}}",
  "metadata": [
    "host.name",
    "transaction.name",
    "transaction.type",
    "observer.version"
  ],
  "metrics": [
    {
      "name": "latency",
      "equation": "A",
      "metrics": [
        {
          "name": "A",
          "aggregation": "avg",
          "field": "transaction.duration.histogram"
        }
      ]
    },
    {
      "name": "throughput",
      "equation": "A / 5",
      "metrics": [
        {
          "name": "A",
          "aggregation": "doc_count"
        }
      ]
    },
    {
      "name": "failedTransRate",
      "equation": "A / B",
      "metrics": [
        {
          "name": "A",
          "aggregation": "doc_count",
          "filter": "event.outcome: \"failure\""
        },
        {
          "name": "B",
          "aggregation": "doc_count",
          "filter": "event.outcome: *"
        }
      ]
    }
  ]
}
```
Query the history with:
```JSON
POST .entities-observability.history-v1.*/_search?track_total_hits=true
{
  "sort": [
    {
      "@timestamp": {
        "order": "desc"
      }
    }
  ]
}
```
and query the latest with:
```JSON
POST .entities-observability.latest-v1.*/_search?track_total_hits=true
{}
```

You should see `transaction.name` with a list of transactions and
`transaction.type` with a list of the different transaction types.

Co-authored-by: Kevin Lacabane <kevin.lacabane@elastic.co>

x-pack/plugins/observability_solution/asset_manager/server/lib/entities/helpers/fixtures/entity_definition.ts

@@ -17,7 +17,7 @@ export const entityDefinition = entityDefinitionSchema.parse({
   },
   identityFields: ['log.logger', { field: 'event.category', optional: true }],
   displayNameTemplate: '{{log.logger}}{{#event.category}}:{{.}}{{/event.category}}',
-  metadata: ['tags', 'host.name'],
+  metadata: ['tags', 'host.name', 'host.os.name'],
   metrics: [
     {
       name: 'logRate',

x-pack/plugins/observability_solution/asset_manager/server/lib/entities/ingest_pipeline/__snapshots__/generate_history_processors.test.ts.snap

@@ -83,9 +83,14 @@ Array [
   ctx[\\"tags\\"] = ctx.entity.metadata.tags.keySet();
 }
 if (ctx.entity?.metadata?.host?.name != null) {
-  ctx[\\"host\\"] = new HashMap();
+ if(ctx.host == null)  ctx[\\"host\\"] = new HashMap();
   ctx[\\"host\\"][\\"name\\"] = ctx.entity.metadata.host.name.keySet();
 }
+if (ctx.entity?.metadata?.host?.os?.name != null) {
+ if(ctx.host == null)  ctx[\\"host\\"] = new HashMap();
+ if(ctx.host.os == null)  ctx[\\"host\\"][\\"os\\"] = new HashMap();
+  ctx[\\"host\\"][\\"os\\"][\\"name\\"] = ctx.entity.metadata.host.os.name.keySet();
+}
 ",
     },
   },

x-pack/plugins/observability_solution/asset_manager/server/lib/entities/ingest_pipeline/__snapshots__/generate_latest_processors.test.ts.snap

@@ -26,9 +26,14 @@ Array [
   ctx[\\"tags\\"] = ctx.entity.metadata.tags.data.keySet();
 }
 if (ctx.entity?.metadata?.host?.name.data != null) {
-  ctx[\\"host\\"] = new HashMap();
+ if(ctx.host == null)  ctx[\\"host\\"] = new HashMap();
   ctx[\\"host\\"][\\"name\\"] = ctx.entity.metadata.host.name.data.keySet();
 }
+if (ctx.entity?.metadata?.host?.os?.name.data != null) {
+ if(ctx.host == null)  ctx[\\"host\\"] = new HashMap();
+ if(ctx.host.os == null)  ctx[\\"host\\"][\\"os\\"] = new HashMap();
+  ctx[\\"host\\"][\\"os\\"][\\"name\\"] = ctx.entity.metadata.host.os.name.data.keySet();
+}
 ",
     },
   },

x-pack/plugins/observability_solution/asset_manager/server/lib/entities/ingest_pipeline/generate_history_processors.ts

@@ -22,7 +22,7 @@ function mapDestinationToPainless(destination: string, source: string) {
         .map((s) => `["${s}"]`)
         .join('')} = ctx.entity.metadata.${source}.keySet();`;
     }
-    return `${acc}\n  ctx${parts
+    return `${acc}\n if(ctx.${parts.slice(0, currentIndex + 1).join('.')} == null)  ctx${parts
       .slice(0, currentIndex + 1)
       .map((s) => `["${s}"]`)
       .join('')} = new HashMap();`;

x-pack/plugins/observability_solution/asset_manager/server/lib/entities/ingest_pipeline/generate_latest_processors.ts

@@ -16,7 +16,7 @@ function mapDestinationToPainless(destination: string, source: string) {
         .map((s) => `["${s}"]`)
         .join('')} = ctx.entity.metadata.${source}.data.keySet();`;
     }
-    return `${acc}\n  ctx${parts
+    return `${acc}\n if(ctx.${parts.slice(0, currentIndex + 1).join('.')} == null)  ctx${parts
       .slice(0, currentIndex + 1)
       .map((s) => `["${s}"]`)
       .join('')} = new HashMap();`;

x-pack/plugins/observability_solution/asset_manager/server/lib/entities/transform/__snapshots__/generate_history_transform.test.ts.snap

@@ -49,6 +49,12 @@ Object {
           "size": 1000,
         },
       },
+      "entity.metadata.host.os.name": Object {
+        "terms": Object {
+          "field": "host.os.name",
+          "size": 1000,
+        },
+      },
       "entity.metadata.tags": Object {
         "terms": Object {
           "field": "tags",

x-pack/plugins/observability_solution/asset_manager/server/lib/entities/transform/__snapshots__/generate_latest_transform.test.ts.snap

@@ -65,6 +65,23 @@ Object {
           },
         },
       },
+      "entity.metadata.host.os.name": Object {
+        "aggs": Object {
+          "data": Object {
+            "terms": Object {
+              "field": "host.os.name",
+              "size": 1000,
+            },
+          },
+        },
+        "filter": Object {
+          "range": Object {
+            "event.ingested": Object {
+              "gte": "now-1m",
+            },
+          },
+        },
+      },
       "entity.metadata.tags": Object {
         "aggs": Object {
           "data": Object {