Refactor ApprovalRules::GroupFinder interface

Everyone can contribute. Help move this issue forward while earning points, leveling up and collecting rewards.

• Close this issue

Finder classes typically only have a single public execute instance method.

ApprovalRules::GroupFinder has many public methods and none of them are execute 😬 https://gitlab.com/gitlab-org/gitlab/-/blob/38ad335189a1080c85c836716469d9774802ce41/ee/app/finders/approval_rules/group_finder.rb#L15-26)

We should refactor ApprovalRules::GroupFinder to have an interface consistent with other Finder classes.