Update MultipleDatabase cop to allow some methods

What does this MR do and why?

Related issue: #350191 (closed)

Update the Database/MultipleDatabases cop to have an allowlist of methods that are safe to call on ActiveRecord::Base. For now there is only one method added: no_touching, which is safe to call even with multiple databases configured.

Also remove offending files from the rubocop todo list based on their usage of no_touching being considered safe.

How to set up and validate locally

We can verify that ActiveRecord::Base.no_touching is safe to use with multiple databases.

1. Setup multiple databases according to https://docs.gitlab.com/ee/development/database/multiple_databases.html#development-setup
2. Start a rails console with separate connections for main and ci:

   GITLAB_USE_MODEL_LOAD_BALANCING=true rails c

3. First, we can try the behavior without no_touching. If you run the below, you'll see update queries for each object to set the updated_at:

   Project.first.touch; Ci::Pipeline.first.touch

4. Now try with no_touching, and it will load each object but no longer run the update queries:

   ActiveRecord::Base.no_touching { Project.first.touch; Ci::Pipeline.first.touch }

5. We can also try with no_touching only on a specific base model. The following will only apply no_touching to the pipeline model:

   Ci::ApplicationRecord.no_touching { Project.first.touch; Ci::Pipeline.first.touch }

MR acceptance checklist

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