Logging: Cleanup database of `clusters_applications_elastic_stacks` & `clusters_integration_elasticstack` tables

Why are we doing this work

In %15.0, we disabled/removed pod logs by moving it behind a feature flag. After the feature flag is disabled & all application code is removed, the database can be purged of any of the old logging/elastic stack content.

⚠ Removal should take place in %15.2 or later.

Tracking issue for all logging removal work: Monitor:Logging Deprecation (#346485 - closed)

Relevant links

• https://docs.gitlab.com/ee/development/migration_style_guide.html#dropping-a-database-table [can be done in a post-migration in same release as removes all app code]
• https://docs.gitlab.com/ee/development/database/avoiding_downtime_in_migrations.html#dropping-tables

Implementation plan

1. Ensure all dependent application code has been removed
2. Drop clusters_applications_elastic_stacks, clusters_integration_elasticstack tables in a post-migration
3. clean up database dictionary records
4. Include ~"group::configure" in code review

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