Allow all project database records to be indexed

Problem to solve

When Advanced search indexing is enabled, projects are indexed in two scenarios:

• Index limiting is not enabled
• Index limiting is enabled and the project or projects group is selected for indexing

Proposal

Allow all project records only (no associated records) to be indexed and searchable regardless of the limiting setting. There will likely be a good number of specs changes due to all indexing and searching now going to Elasticsearch if it's enabled

Currently the checks for searching and indexing are done in Elastic::ProjectsSearch concern and ApplicationVersionSearch concern

Lastly, update index limiting documentation to make clear that all project info is indexed regardless of the setting.