Move big rule implementations (#18931)
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## Summary
<!-- What's the purpose of the change? What does it do, and why? -->
Here's the part that was split out of #18906. I wanted to move these
into the rule files since the rest of the rules in
`deferred_scope`/`statement` have that same structure of implementations
being in the rule definition file. It also resolves the dilemma of where
to put the comment, at least for these rules.
## Test Plan
<!-- How was it tested? -->
N/A, no test/functionality affected
