[Fleet] Save package policy previous revision on package upgrade (#222779)

## Summary

Closes https://github.com/elastic/ingest-dev/issues/5444

* Add `enablePackageRollback` feature flag
* Save package policy previous revision on package upgrade
* Add `latest_revision` boolean property to
`ingest-package-policies/fleet-package-policies` saved object type
   * Package policy SO are created with `latest_revision: true`
* When a package policy is updated with a new package version, the
previous SO is saved to ES with id `{id}:prev` and `latest_revision:
false`
   * Backfill existing SO with `latest_revision: true`
   * GET logic filters for `latest_revision: true`
* Save package previous version
   * Add `previous_version` property to `epm-packages` saved object type
   * When a package is upgraded to a new version, set `previous_version`

### Testing

* Install an integration on an outdated version (edit the version in the
URL and add the integration).
* Check the package policy SO: it should have been created with
`latest_revision: true`.
* Check the package SO: the `previous_version` property should not be
set.
* Upgrade the integration and upgrade package policies.
* Check the package policy SO: there should now be 2 SO for this package
policy:
   * The updated one with `latest_revision: true` and policy id
* The previous one with `latest_revision: false` and `{policy_id}:prev`
* Check the package SO: the `previous_version` property should be set to
the old version

Note: it seems Fleet only allows upgrading packages to the latest
version (please correct me if that's wrong); for testing two consecutive
updates (e.g. check that only the most recent revision is saved), it
might be necessary to run a custom EPR.

### Checklist

- [x] [Unit or functional
tests](https://www.elastic.co/guide/en/kibana/master/development-tests.html)
were updated or added to match the most common scenarios
- [x] The PR description includes the appropriate Release Notes section,
and the correct `release_note:*` label is applied per the
[guidelines](https://www.elastic.co/guide/en/kibana/master/contributing.html#kibana-release-notes-process)

### Identify risks

Risk of bad requests across Fleet wherever packages or package policies
are queried.

---------

Co-authored-by: kibanamachine <42973632+kibanamachine@users.noreply.github.com>
Co-authored-by: Elastic Machine <elasticmachine@users.noreply.github.com>

packages/kbn-check-mappings-update-cli/current_fields.json

@@ -313,12 +313,9 @@
     "enabled",
     "error",
     "filter",
-    "indexPattern",
     "integrationName",
     "managed",
     "matchers",
-    "matchers.fields",
-    "matchers.values",
     "name",
     "type"
   ],
@@ -373,6 +370,7 @@
     "latest_install_failed_attempts",
     "name",
     "package_assets",
+    "previous_version",
     "verification_key_id",
     "verification_status",
     "version"
@@ -550,6 +548,7 @@
     "enabled",
     "inputs",
     "is_managed",
+    "latest_revision",
     "name",
     "namespace",
     "output_id",
@@ -735,6 +734,7 @@
     "enabled",
     "inputs",
     "is_managed",
+    "latest_revision",
     "name",
     "namespace",
     "output_id",
@@ -841,19 +841,6 @@
     "job.job_id",
     "model_id"
   ],
-  "monitoring-entity-source": [
-    "enabled",
-    "error",
-    "filter",
-    "indexPattern",
-    "integrationName",
-    "managed",
-    "matchers",
-    "matchers.fields",
-    "matchers.values",
-    "name",
-    "type"
-  ],
   "monitoring-telemetry": [
     "reportedClusterUuids"
   ],

packages/kbn-check-mappings-update-cli/current_mappings.json

@@ -1256,6 +1256,9 @@
         "dynamic": false,
         "properties": {}
       },
+      "previous_version": {
+        "type": "keyword"
+      },
       "verification_key_id": {
         "type": "keyword"
       },
@@ -1835,6 +1838,9 @@
       "is_managed": {
         "type": "boolean"
       },
+      "latest_revision": {
+        "type": "boolean"
+      },
       "name": {
         "type": "keyword"
       },
@@ -2438,6 +2444,9 @@
       "is_managed": {
         "type": "boolean"
       },
+      "latest_revision": {
+        "type": "boolean"
+      },
       "name": {
         "type": "keyword"
       },