Remove gitlab-grit as a transitive dependency of GitLab

What does this MR do?

gitlab-grit is a fork of the original grit gem. In the post-Gitaly world, it's an anachronism, and ideally, we'd be able to remove it from the list of gems we need to support.

There are a few dependencies of GitLab that, themselves, depend on gitlab-grit. This MR inlines the required parts and drops the dependencies, so we can remove this gem from the Gemfile for good.

Following up from this, we should deprecate and archive any of these projects that are GitLab-owned.

What are the relevant issue numbers?

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Documentation created/updated
• Tests added for this feature/bug
• Conforms to the code review guidelines
• Conforms to the merge request performance guidelines
• Conforms to the style guides
• Conforms to the database guides

Closes #44361 (closed)