Finish the permissions table breakout into categories

What does this MR do?

Finish the work Joe started to break the generic tables out into meaningful categories as outlined in Finalize table breakout of categories for the p... (#482035 - closed)

Also, made some other changes/fixes related to this restructuring:

• The duplicate headings for groups and projects will prevent anchor links to the groups from functioning properly. Added "group permissions" and "project permission" to headings to resolve this. It's not as "clean" looking, but it's functional, and will help users scan the page more easily.
• Moved the GitLab Duo permissions up so they don't break the alphabetical order
• Promoted "Subgroup permissions" from H3 to H2.
• Removed unnecessary links from the tables, when they were just the same links as the context paragraph repeated over and over.

Related issues

#482035 (closed)

Author's checklist

• Optional. Consider taking the GitLab Technical Writing Fundamentals course.
• Follow the:
  • Documentation process.
  • Documentation guidelines.
  • Style Guide.
• If you're adding a new page, add the product availability details under the H1 topic title.
• If you are a GitLab team member, request a review based on:
  • The documentation page's metadata.
  • The associated Technical Writer.

If you are a GitLab team member and only adding documentation, do not add any of the following labels:

• ~"frontend"
• ~"backend"
• ~"type::bug"
• ~"database"

These labels cause the MR to be added to code verification QA issues.

Reviewer's checklist

Documentation-related MRs should be reviewed by a Technical Writer for a non-blocking review, based on Documentation Guidelines and the Style Guide.

If you aren't sure which tech writer to ask, use roulette or ask in the #docs Slack channel.

• If the content requires it, ensure the information is reviewed by a subject matter expert.
• Technical writer review items:
  • Ensure docs metadata is present and up-to-date.
  • Ensure the appropriate labels are added to this MR.
  • Ensure a release milestone is set.
  • If relevant to this MR, ensure content topic type principles are in use, including:
    • The headings should be something you'd do a Google search for. Instead of Default behavior, say something like Default behavior when you close an issue.
    • The headings (other than the page title) should be active. Instead of Configuring GDK, say something like Configure GDK.
    • Any task steps should be written as a numbered list.
    • If the content still needs to be edited for topic types, you can create a follow-up issue with the docs-technical-debt label.
• Review by assigned maintainer, who can always request/require the reviews above. Maintainer's review can occur before or after a technical writer review.