[clang] [llvm] [libclang/python][ci] Add release Clang Python Bindings CI workflow (PR #168234)

[Ryan Mast via llvm-commits]

nightlark wrote:

Here are some test runs of the workflow that I did in my fork:
* https://github.com/nightlark/llvm-project/actions/runs/19394995716
    * workflow_dispatch release version 20.8.5 (fake tag in my fork)
    * checks out the corresponding llvmorg tag
    * uploaded dist artifacts have 20.8.5 version number in them
    * skips release step because the repo isn't owned by llvm, it's a fork
* https://github.com/nightlark/llvm-project/actions/runs/19394988110
    * workflow_dispatch with no release version specified
    * checks out the latest commit (same as PR workflow that ran)
    * uploaded dist artifacts (with a post/dev version that doesn't really matter since it will never be published to PyPI)
    * skips release step because repo isn't owned by llvm, it's a fork (and no version number was given)
* https://github.com/nightlark/llvm-project/actions/runs/19395404575
    * temporarily removed the condition for the repository owner being the llvm org
    * skips the release step because no version was specified (avoids unintentional upload of an untagged version)
* https://github.com/nightlark/llvm-project/actions/runs/19395406366
    * temporarily removed the condition for the repository owner being the llvm org
    * tries to run the release step because a version input is specified, tries to run the permissions check but fails due to not having a suitable user token; similar to the upload step failing there due to the permissions check actually failing and thus preventing an upload)

https://github.com/llvm/llvm-project/pull/168234