Add enabled git access protocol option to groups

What does this MR do and why?

Describe in detail what your merge request does and why.

Adds support for configuring git access protocols at the group level. Currently this only works on the root group and not descendants, but this could be updated in future if required.

Closes https://gitlab.com/gitlab-org/gitlab/-/issues/364840

Feature flag

The group setting is hidden behind the group_level_git_protocol_control feature flag. This is to aid in rolling out this change and will be removed quickly afterwards.

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