[clang-tools-extra] Adding first version for which clang-tidy checks and their options are available (PR #162937)

[Baranov Victor via cfe-commits]

vbvictor wrote:

> Does that mean I should make a separate PR with only this script for people to review it? Or upload it somewhere (Gist?) and share it for review (if so, which platform should I share it on? Discourse? Discord?).
Regardless of that, I still have some modifications/cleanups to do regarding it and I also need to make sure it follows [LLVM guidelines](https://llvm.org/docs/CodingStandards.html#python-version-and-source-code-formatting).

I think we can put it as a PR in LLVM, it's the most convenient place to look at code. The benefits of review are:

- We (clang-tidy team) can verify that it works correctly and have a dedicated place to share opinions.
- If we find out a bug (maybe by user bug report), we can fix the script ourselves and rerun it over all documents to fix everything. This is particularly important in case you will not be available. If we don't store it here, your Gist can be deleted because you got hacked/deleted etc... I think we as a project can't depend on 3rd party software that has a single point of failure.

https://github.com/llvm/llvm-project/pull/162937