Add script to cut release branch (#2567)

Summary:
Pull Request resolved: https://github.com/pytorch/executorch/pull/2567

Step 1 of release process: Create a release branch.

The branch is named with `release/MAJOR.MINOR`.

From executorch root, run `./scripts/release/cut-release-branch.sh` will cut a release branch off stable branch (`viable/strict`) by default. Use `GIT_BRANCH_TO_CUT_FROM=main ./scripts/release/cut-release-branch.sh` to cut off `main` branch.

imported-using-ghimport

Test Plan: Imported from OSS

Reviewed By: huydhn

Differential Revision: D55208762

Pulled By: guangy10

fbshipit-source-id: cdf676586266b475a74d42c1ef31f93122657925