Moved several project-related topics into new topic

What does this MR do?

This MR is a first attempt to make the top-level Projects page a "landing page" and moves tasks into a new topic. It also brings in topics that were in a "Create a project" topic and pulls them into the new topic as well, so all the create, edit, delete topics are in one.

Will need more work, but this is the beginning of the move.

Details

• Created a new topic called working_with_projects.md
• Redirected: /gitlab-basics/create-project.md and put the content in the new working_with_projects.md file.
• Redirected: /gitlab-basics/fork-project.md and put the content in the new working_with_projects.md file.
• Moved content from the top-level Projects page and added it to the new working_with_projects.md file.
• Moved Project aliases topic from the main Projects page to the Migrating Projects page.
• Moved Redirects when changing repository paths from the main Projects page to the Repositories page.

Things I didn't do:

• Edit any text except for one intro sentence very slightly.
• Remove that Go content from the Projects page, because I'm not sure where it should go.
• There is a remaining straggler topic (Project activity analytics overview) at the end of the Projects page that I also don't know where to put yet. I think it should go in Analytics section, but waiting to move.
• There is another topic that's not in the nav called Forking workflow. This also seems to be a bit of a duplicate.
• There are language inconsistencies between importing a project and migrating a project. The folder is called import but I think maybe we've standardized on migrate. Not sure.
• Style note: When you say "Create" you don't also have to say "new." It's implied.
• Another style note: We should check our usage of "repository" vs "project." Especially when it comes to migrating/importing.
• We should consider how often we use "in GitLab" in topic titles. This is the GitLab help, so it's probably not needed unless there is a chance of confusion.

Related issues

Related to: gitlab-docs!1504 (merged)

Related to: #300312 (closed)

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