[clang] [llvm] [NFC][analyzer] Extract bounds checking library (PR #202372)

[Donát Nagy via cfe-commits]

NagyDonat wrote:

> > in hindsight it might have been better to start with a "pure redesign" commit that leaves everything in ArrayBoundChecker.cpp
> 
> I think this approach would make the review much easier.

I see that it _would have been_ better to start with that initially, but I'm not sure that it _is still_ the better approach now that we have this PR.

@Xazax-hun @steakhal Should I abandon this PR and restart the refactoring with that different approach?

https://github.com/llvm/llvm-project/pull/202372