Until #1306 is resolved (some spilling/regalloc issue with larger FPR register banks), this removes FPR32 support. Only Wasm's `i64x2.mul` was using this register class and that instruction is predicated on AVX512 support; for the time being, that instruction will have to make do with the 16 FPR registers.
This is the wasmtime-jit crate, which contains JIT-based execution
for wasm, using the wasm ABI defined by wasmtime-environ and the
runtime support provided by wasmtime-runtime.