Draft: Add v2 approval rule associations to protected branch and security pol

Gavin Hinfeyrequested to merge
512606-create-approval-rule-protected-branch-security-policy-joins into master

What does this MR do and why?

Adds new approval rule associations to protected branch and security policies for new approval rule architecture.

References

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Issue: https://gitlab.com/groups/gitlab-org/-/issues/512606+
Epic: Rearchitecting Approval Rules (&12955)
POC: Draft: [ci skip][DO NOT MERGE][PoC] Start of Po... (!171114 - closed)

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Related to #512606 (closed)

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