PyTorch release scripts performing branch cut and applying release only changes

These are a collection of scripts that are to be used for release activities.

NOTE: All scripts should do no actual work unless the DRY_RUN environment variable is set to disabled. The basic idea being that there should be no potential to do anything dangerous unless DRY_RUN is explicitly set to disabled.

Order of Execution

1. Run cut-release-branch.sh to cut the release branch
2. Run apply-release-changes.sh to apply release only changes to create a PR with release only changes similar to this PR

Promoting packages

Scripts for Promotion of PyTorch packages are under test-infra repository. Please follow README.md