[Fleet] Fix crashes when installing a package with a lot of saved objects

[xcrzx]

Resolves: #147695, #148174
Related to: #145851, #137420

Summary

This PR improves the stability of the Fleet packages installation process with many saved objects.

1. Changed mappings of the installed_kibana and package_assets fields from nested to object with enabled: false. Values of those fields were retrieved from _source, and no queries or aggregations were performed against them. So the mappings were unused, while during the installation of packages containing more than 10,000 saved objects, an error was thrown due to the nested field limitations:

   Error installing security_detection_engine 8.4.1: The number of nested documents has exceeded the allowed limit of 
   [10000].
   This limit can be set by changing the [index.mapping.nested_objects.limit] index level setting.
   

2. Improved the deletion of previous package assets by switching from sending multiple savedObjectsClient.delete requests in parallel to a single savedObjectsClient.bulkDelete request. Multiple parallel requests were causing the Elasticsearch cluster to stop responding for some time; see this ticket for more info.

Before

After

[elasticmachine]

Pinging @elastic/fleet (Team:Fleet)

[kpollich]

Code changes look small in scope, but with big impact. Really appreciate the improvements here, and the before/after traces you provided. LGTM 🚀

[kibana-ci]

💛 Build succeeded, but was flaky

• Buildkite Build
• Commit: 31c46ec

Failed CI Steps

• Jest Tests #7

Test Failures

• [job] [logs] Jest Tests #7 / AllCasesListGeneric Actions Row actions should disable row actions when bulk selecting all cases
• [job] [logs] Jest Tests #7 / AllCasesListGeneric Actions Row actions should disable row actions when selecting a case
• [job] [logs] Jest Tests #7 / AllCasesListGeneric Actions Row actions update the status of a case: critical

Metrics [docs]

Saved Objects .kibana field count

Every field in each saved object type adds overhead to Elasticsearch. Kibana needs to keep the total field count below Elasticsearch's default limit of 1000 fields. Only specify field mappings for the fields you wish to search on or query. See https://www.elastic.co/guide/en/kibana/master/saved-objects-service.html#_mappings

id	before	after	diff
epm-packages	28	22	-6

History

• 💚 Build #97227 succeeded 5d3d24b0644c9d2e1e158edfbe8d14e2e2ac89b7
• 💔 Build #97207 failed 36cc2bfb528045785f17a54827a2110ebef0c3ce

To update your PR or re-run it, just comment with:
@elasticmachine merge upstream

cc @xcrzx