[clang] [clang][CIR][doc] Add auto-generated ClangIR documentation (PR #190354)

[Aaron Ballman via cfe-commits]

AaronBallman wrote:

> > Hi @Lancern, I see (locally) the following error after this change with Python 3.8.
> > ```
> > 
> > docs/CIR/_raw/PostProcessCIRDocs.py", line 45
> > 
> >     index_content += f"""
> > 
> >                      ^
> > 
> > SyntaxError: f-string expression part cannot include a backslash
> > ```
> 
> Ooops... obviously f-string is not available in Python 3.8 . Do we have a requirement on the minimal Python version we have to support?

https://llvm.org/docs/GettingStarted.html#software, so Python 3.8 is the current minimum required. There was an RFC about bumping it https://discourse.llvm.org/t/rfc-upgrading-llvm-s-minimum-required-python-version/88605 but it didn't seem to gain consensus. 

https://github.com/llvm/llvm-project/pull/190354