Draft: Refactor Authz::Roles class (2 of 3)

What does this MR do and why?

Refactor Authz::Roles class

Moving Authz::Role.access_level_encompasses? to Gitlab::Access.level_encompasses? as a first step to refactor role comparison methods.

original MR: !210959 (closed)

part of: https://gitlab.com/gitlab-org/gitlab/-/issues/574071

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