[Fleet] Update input package data stream check to only look for Fleet-managed data streams

[kpollich]

Currently, this check will return true if any managed data stream exists with the same index pattern defined by an input package policy:

kibana/x-pack/plugins/fleet/server/services/epm/packages/install.ts

Lines 1352 to 1354 in 19818f2

	const existingDataStreamsAreFromDifferentPackage = existingDataStreams.some(
	(ds) => ds._meta?.package?.name !== pkgInfo.name
	);

The intent behind this check is to prevent users from routing custom logs documents to other integration data streams that have their own index settings, mappings, etc defined. Pushing custom logs documents into an integration's ingest pipeline could result in pipeline errors, for example.

We should potentially only be checking Fleet-managed (e.g. managed_by: "fleet") data streams instead of any managed data stream matching the given index pattern.

In cases where users ingest data outside of the context of Fleet, this check can result in false positives, e.g.

1. Run the following in Kibana dev tools

POST logs-generic-default/_doc
{
  "@timestamp": "2024-05-15T00:00:00.000Z",
  "message": "foo"
}

2. Check the data stream that was created, e.g.

GET _data_stream/logs-*

// Response
{
  "data_streams": [
    {
      "name": "logs-generic-default",
      "timestamp_field": {
        "name": "@timestamp"
      },
      "indices": [
        {
          "index_name": ".ds-logs-generic-default-2024.05.15-000001",
          "index_uuid": "dqi4bbNAR0CJ1WtdgIgVgQ",
          "prefer_ilm": true,
          "ilm_policy": "logs",
          "managed_by": "Index Lifecycle Management"
        }
      ],
      "generation": 1,
      "_meta": {
        "description": "default logs template installed by x-pack",
        "managed": true
      },
      "status": "YELLOW",
      "template": "logs",
      "ilm_policy": "logs",
      "next_generation_managed_by": "Index Lifecycle Management",
      "prefer_ilm": true,
      "hidden": false,
      "system": false,
      "allow_custom_routing": false,
      "replicated": false,
      "rollover_on_write": false,
      "failure_store": {
        "enabled": false,
        "rollover_on_write": false,
        "indices": []
      }
    }
  ]
}

3. Attempt to create a custom logs policy using the generic dataset

4. Observe the error thrown in the code path linked above

[elasticmachine]

Pinging @elastic/fleet (Team:Fleet)