Combine doc pages about sharing projects

Problem to solve

gitlab-docs!4724 (comment 1875852727)

There are three page that document how to share projects:

• Organize work with projects > Share a project with a group
• Manage your organization > Sharing projects and groups
• Manage your organization > Members > Add groups to a project

These page have partially duplicate information, and it's difficult to find all the information related to this behavior because it's documented on different pages.

Proposal

Consolidate the information from the three pages ideally into one.

Who can address the issue

TW for grouptenant scale

Other links/references