create a cherry-pick scripts for release process

[jgao54]

This cherry-pick executes the following steps:

1. fetch the release tag and the cherry-pick commit
2. lazily create release branch release/ if it doesn't exist
3. create cherry-pick branch cherry-pick- off the HEAD of release/ branch and cherry-pick the commit to it
4. wait for user to handle merge conflicts (if conflict detected)
5. push the cherry-pick branch and open a github compare link against it

Notes:

• by default, release tags are created against main branch. When cherry-pick script is used, release tags should be created against the release branch (i.e. release/<release-tag>) the cherry-pick is intended for.
• cherry-picking multiple commits against the same release branch is supported; it just requires running the script multiple times sequentially.
• another benefit for using release branch for cherry-picks is to make the changes safer. release branch CI can be used to build more confidence over complex reverts / forward fixes.

Test: ran script locally to test a few scenarios:

• happy-path flow
• merge conflict handling
• script exits when CP commit is invalid (i.e. already in release branch history)

TODO: validate on Linux