[clang] [flang] [llvm] [mlir] [Support][NFC] Move OptimizationLevel to the Support directory (PR #157057)

[Sergei Barannikov via cfe-commits]

s-barannikov wrote:

I always thought of ADT and Support libraries as being useful for other projects, OptLevel seems too llvm-specific to me. Could CodeGen directory be a better choice?


https://github.com/llvm/llvm-project/pull/157057