WASM is the only architecture we use `intrinsics::` for. We probably
don't want to do this for any other architectures since it is better to
use assembly, or work toward getting the functions available in `core`.
To more accurately reflect the relationship between arch and intrinsics,
make wasm32 an `arch` module and call the intrinsics from there.
Update test traits to support `f16` and `f128`, as applicable. Add the
new routines (`fabs` and `copysign` for `f16` and `f128`) to the list of
all operations.
Update the script to produce, in addition to the simple text list, a
JSON file listing routine names, the types they work with, and the
source files that contain a function with the routine name. This gets
consumed by another script and will be used to determine which extensive
CI jobs to run.
