[clang] [flang] [llvm] [openmp] [flang][driver] rename flang-new to flang (PR #110023)

[Peter Klausler via cfe-commits]

klausler wrote:

There are multiple weird failures in llvm-test-suite where clang++ complains about unknown options that look like they're slang-only options.  Did you run llvm-test-suite before merging?  Please check.  These failures are going to cause build bot failures shortly in the clang-*-2stage builds if not repaired or reverted.

https://github.com/llvm/llvm-project/pull/110023