Port some floating point options to new option marshalling infrastructure

This ports a number of OpenCL and fast-math flags for floating point
over to the new marshalling infrastructure.

As part of this, `Opt{In,Out}FFlag` were enhanced to allow other flags to
imply them, via `DefaultAnyOf<>`. For example:
```
defm signed_zeros : OptOutFFlag<"signed-zeros", ...,
  "LangOpts->NoSignedZero",
  DefaultAnyOf<[cl_no_signed_zeros, menable_unsafe_fp_math]>>;
```
defines `-fsigned-zeros` (`false`) and `-fno-signed-zeros` (`true`)
linked to the keypath `LangOpts->NoSignedZero`, defaulting to `false`,
but set to `true` implicitly if one of `-cl-no-signed-zeros` or
`-menable-unsafe-fp-math` is on.

Note that the initial patch was written Daniel Grumberg.

Differential Revision: https://reviews.llvm.org/D82756