Update sharing and permissions section

What does this MR do?

Updates the description for project settings, what you see in a repo when you select Settings > General. The current doc is shown in today's version of https://docs.gitlab.com/ee/user/project/settings/#sharing-and-permissions .

I created this MR based on the following issue: #39492 (closed)

In this MR, I've

• Reduced the coverage of the screenshot (it covered too much info and risks becoming out of date with every UI change)
• Included a table that explains the functionality of each option
• Explained interactions between options, below the table.

Screenshots

Most of the change is built in these screenshots:

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry Unneeded
• Documentation (if required)
• Code review guidelines
• Style guides
• Separation of EE specific content

Availability and Testing

Note: there are test failures that I think are unrelated to docs:

• compile-assets-pull-cache
• compile-assets-pull-cache-foss
• gitlab:assets:compile pull-cache

I'd appreciate advice on how to omit these jobs from the MR pipeline.