[clang] [clang] Assert the enum FPOpts and LangOpts fit into the storage (PR #126166)

[Florian Mayer via cfe-commits]

fmayer wrote:

@zahiraam the default of the `ComplexRange`, `CX_None` does overflow the `2` storage bits. That means we were probably still using `CX_Full` (4 should overflow to `0`) even after https://github.com/llvm/llvm-project/pull/78330 (I am not sure why "make sure why that changed the default in the first place). Also it's impossible to manually choose `CX_None`.

https://github.com/llvm/llvm-project/pull/126166