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

[Gábor Horváth via cfe-commits]

Xazax-hun wrote:

This PR is not just moving code between files, many of the facilities it introduces like CheckResult did not exist before.

It might make sense to do the move and the redesign in two steps but in this case I'd prefer to start with a PR that purely just moves code. Currently, there are some arbitrary changes you made to the code and some you rejected and there seems to be no clear distinction what changes are OK and what are not and why. 

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