Go through codebase and consolidate checkout steps
Recently, @cpuhrsch noticed that going to viable/strict still didn't resolve upstream failures for lint. This is because we didn't check out the head SHA for those GHA (we missed it last time).
This PR attempts to do some consolidation and fix that problem to make viable/strict more reliable.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/75199
Approved by: https://github.com/cpuhrsch, https://github.com/seemethere, https://github.com/malfet
