[8.14] [UnifiedHistogram] Improve breakdown chart when values for the field are missing (#181013) (#181433)

# Backport

This will backport the following commits from `main` to `8.14`:
- [[UnifiedHistogram] Improve breakdown chart when values for the field
are missing (#181013)](https://github.com/elastic/kibana/pull/181013)

<!--- Backport version: 9.4.3 -->

### Questions ?
Please refer to the [Backport tool
documentation](https://github.com/sqren/backport)

<!--BACKPORT [{"author":{"name":"Julia
Rechkunova","email":"julia.rechkunova@elastic.co"},"sourceCommit":{"committedDate":"2024-04-23T12:55:30Z","message":"[UnifiedHistogram]
Improve breakdown chart when values for the field are missing
(#181013)\n\n## Summary\r\n\r\nThis PR changes Lens configuration to
visualize data even if values for\r\nthe \"Breakdown by\" field are not
provided.\r\n\r\nBefore:\r\n<img width=\"600\" alt=\"Screenshot
2024-04-17 at 11 34
41\"\r\nsrc=\"02957896-4d5b-4a99-b09b-076ee962c219\">\r\n\r\nAfter:\r\n<img
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Improve breakdown chart when values for the field are
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Improve breakdown chart when values for the field are missing
(#181013)\n\n## Summary\r\n\r\nThis PR changes Lens configuration to
visualize data even if values for\r\nthe \"Breakdown by\" field are not
provided.\r\n\r\nBefore:\r\n<img width=\"600\" alt=\"Screenshot
2024-04-17 at 11 34
41\"\r\nsrc=\"02957896-4d5b-4a99-b09b-076ee962c219\">\r\n\r\nAfter:\r\n<img
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Improve breakdown chart when values for the field are missing
(#181013)\n\n## Summary\r\n\r\nThis PR changes Lens configuration to
visualize data even if values for\r\nthe \"Breakdown by\" field are not
provided.\r\n\r\nBefore:\r\n<img width=\"600\" alt=\"Screenshot
2024-04-17 at 11 34
41\"\r\nsrc=\"02957896-4d5b-4a99-b09b-076ee962c219\">\r\n\r\nAfter:\r\n<img
width=\"600\" alt=\"Screenshot 2024-04-17 at 11 35
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BACKPORT-->

Co-authored-by: Julia Rechkunova <julia.rechkunova@elastic.co>

src/plugins/unified_histogram/public/services/lens_vis_service.attributes.test.ts

@@ -240,7 +240,7 @@ describe('LensVisService attributes', () => {
                         "label": "Top 3 values of extension",
                         "operationType": "terms",
                         "params": Object {
-                          "missingBucket": false,
+                          "missingBucket": true,
                           "orderBy": Object {
                             "columnId": "count_column",
                             "type": "column",

src/plugins/unified_histogram/public/services/lens_vis_service.ts

@@ -378,7 +378,7 @@ export class LensVisService {
             },
             orderDirection: 'desc',
             otherBucket: true,
-            missingBucket: false,
+            missingBucket: true,
             parentFormat: {
               id: 'terms',
             },