[clang][dataflow] Add base types for building dataflow analyses

This is part of the implementation of the dataflow analysis framework.
See "[RFC] A dataflow analysis framework for Clang AST" on cfe-dev.

Reviewed By: ymandel, xazax.hun, gribozavr2

Differential Revision: https://reviews.llvm.org/D114234

GitOrigin-RevId: 6e2aecd759dc3f8bf664323388365ac234271e9b
7 files changed