Remove name suggestion generator

What does this MR do and why?

This is one of several MRs to remove name from metric definitions. See: #411602 (closed)

This MR removes the name suggestion generator and the test that belongs to it.

Documentation will be updated in a separate MR.

How to set up and validate locally

1. Run bundle exec rails generate gitlab:usage_metric_definition counts.my_count --dir=7d --class_name=CountIssues
2. Verify that the generated file doesn't have a name key.

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.

Related to #411602 (closed)