GraphQL enforce `.` at end of description strings [RUN AS-IF-FOSS]

What does this MR do?

Previously our GraphQL styleguide stated that description strings should not end in periods. Descriptions provided by ruby-graphql objects all do end in periods, so our overall API is inconsistent in how it presents its schema descriptions.

This change switches our description styleguide to recommend that we add periods to the end of description strings due to this being the standard that types from graphql-ruby follow.

It also adds to the existingGraphQL/Descriptions cop to enforce this and corrects all offenses.

There is a despairingly large amount of changes in this MR due to correcting the existing offenses. To help review the code changes that are not the offense corrections, collapse the app/graphql and ee/app/graphql directories in the diff file viewer !45731 (diffs).

Does this MR meet the acceptance criteria?

Conformity

• [-] Changelog entry
• Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• [-] Database guides
• [-] Separation of EE specific content

Availability and Testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• [-] Tested in all supported browsers
• [-] Informed Infrastructure department of a default or new setting change, if applicable per definition of done