This change introduces lowering from CIR to LLVM IR of global integer
and floating-point variables, using defaults for attributes that aren't yet
implemented.
This adds a .clang-tidy file to the clang/lib/CIR/FrontendAction
directory, moves and updates the incorrectly located
include/clang/CIR/FrontendAction .clang-tidy file, and updates two files
from a recent commit to bring them into conformance with previously
agreed upon rules for where to use LLVM naming conventions and where to
use MLIR naming conventions.
Create the skeleton framework for lowering from ClangIR to LLVM IR. This
initial implementation just creates an empty LLVM IR module. Actual
lowering of even minimal ClangIR is deferred to a later patch.
