Move the Members section from settings to the side nav for projects

What does this MR do?

• Moves the Project membership management from the settings area for privileged users to the side navigation to better align with current Group membership management
  • Before it was only a top level tab if the user didn't have settings. This will make it top level for all users.
• Removes legacy project_settings_members_path which was merely a redirect to project_project_members_path

Screenshots

Current

• Group Membership is directly accessible from side nav.
• Project Membership is nested under Settings.

Group Membership	Project Membership

Updated

• No Change to Group Membership.
• Project Membership now matches Group Membership nav.

Group Membership	Project Membership not collapsed	Project Membership collapsed	Project Settings

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• [-] Database guides
• [-] Separation of EE specific content

Availability and Testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• [-] Tested in all supported browsers
• [-] Informed Infrastructure department of a default or new setting change, if applicable per definition of done

Security

If this MR contains changes to processing or storing of credentials or tokens, authorization and authentication methods and other items described in the security review guidelines:

• [-] Label as security and @ mention @gitlab-com/gl-security/appsec
• [-] The MR includes necessary changes to maintain consistency between UI, API, email, or other methods
• [-] Security reports checked/validated by a reviewer from the AppSec team

Contributes to #214102