Reorganize group member management into tabs

What does this MR do?

Improves UX by reorganizing the group members management page into tabs. It moves "Members", "Groups", "Pending", and "Access requests" into tabs.

• See #229830 (closed)
• As a bonus this MR fixes - #207977 (closed)
• There is an existing issue that causes the Invited tab to disappear when searching Members. I created #233541 (closed) for it here

Screenshots

Page	Before	After
Members
Members - mobile
Linked groups	N/A
Linked groups - mobile	N/A
Invited
Invited - mobile
Access requests	N/A
Access requests - mobile	N/A

Local testing

1. Create a group
2. Navigate to Group -> Members

How to add a group

1. Navigate to Group -> Members
2. Click the Invite group tab

How to add a pending member

1. Navigate to Group -> Members
2. In the GitLab member or Email address enter an email that a user does not already own
3. Click Invite "example@test.com" by email

How to request access to a group

1. Log in (or impersonate) a user that doesn't already have access to the group
2. Navigate to the group overview
3. Click Request access located below the group name

Seeding

Instead of manually adding users with the above methods you can also seed the database with these rake tasks.

Note: you need to check Disable email notifications in Group -> Settings -> General -> Permissions, LFS, 2FA

ee/lib/tasks/gitlab/seed_group_members.rake

namespace :gitlab do
  # Your group ID
  GROUP_ID = 178

  task :seed_group_members => :gitlab_environment do
    group = ::Group.find(GROUP_ID)
    51.times do
      user = FactoryBot.create(:user, email: FFaker::Internet.email, name: FFaker::Name.name, username: FFaker::Internet.user_name)
      group.add_guest(user)
    end
  end

  task :seed_invited_group_members => :gitlab_environment do
    group = ::Group.find(GROUP_ID)
    51.times do
      FactoryBot.create(:group_member, group: group, user_id: nil, invite_token: 'xxx', invite_email: FFaker::Internet.email)
    end
  end

  task :seed_group_access_requests => :gitlab_environment do
    group = ::Group.find(GROUP_ID)
    5.times do
      user = FactoryBot.create(:user, email: FFaker::Internet.email, name: FFaker::Name.name, username: FFaker::Internet.user_name)
      FactoryBot.create(:group_member, :access_request, group: group, user: user)
    end
  end
end

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