Rename elasticsearch_* settings in UI to Advanced search

Background

When advanced search was first introduced, the feature only supported integration with Elasticsearch. As a result, much of the initial code (think class names, etc) and UI (including settings names) are named with some flavor of elastic or elasticsearch in names and titles. Advanced search now supports OpenSearch as well as Elasticsearch.

Proposal

Since the feature supports integration with Elasticsearch OR OpenSearch, any user facing messaging (including Admin UI, rake tasks and documentation) should not specify Elasticsearch in the name of things or messaging. All references to Elasticsearch in the admin UI and rake tasks should be converted to reference the feature name instead.

• Change Admin UI - Search - Advanced search settings

  existing	proposed
  Elasticsearch indexing	Indexing for advanced search
  Pause Elasticsearch indexing	Pause indexing for advanced search
  Search with Elasticsearch enabled	Search with advanced search

• Update all documentation references:
  • Elasticsearch indexing: https://gitlab.com/search?search=Elasticsearch+indexing+file:.md&group_id=9970&project_id=278964&scope=blobs
  • Pause Elasticsearch indexing: https://gitlab.com/search?search=Pause+Elasticsearch+indexing+file:.md&group_id=9970&project_id=278964&scope=blobs
  • Search with Elasticsearch enabled: https://gitlab.com/search?search=Search+with+Elasticsearch+enabled+file:.md&group_id=9970&project_id=278964&scope=blobs
• Evaluate the log messaging in the elastic rake task and update to reference feature. Change the following:

  existing	proposed
  WARNING: 'elasticsearch_pause_indexing; is enabled. This setting will be disabled to complete indexing	WARNING: Indexing for advanced search is paused. This setting will be disabled to complete indexing.
  Setting 'elasticsearch_indexing' is disabled. This setting will been enabled to complete indexing.	Indexing for advanced search is disabled. This setting will been enabled to complete indexing.
  Setting 'elasticsearch_indexing is disabled. Migrations may not be accurate.	Indexing for advanced search is disabled. Migrations may not be accurate.

The following discussion from !204258 (merged) should be addressed:

• @terrichu started a discussion:

  Honestly, I'd like to change all of these settings to visually say this:

  • Elasticsearch indexing --> Advanced search indexing
  • Pause Elasticsearch indexing --> Pause advanced search indexing
  • Search with Elasticsearch enabled --> Search with advanced search enabled

  Is that something I could do in this MR? I hesitate to make a change like this without more communication from us. I don' think it's breaking to change the UI and I'm not recommending to change the backend name of the settings. Though it's unfortunate that the names include elasticsearch. WDYT?