[mono][llvm] Improve LLVM 9 compatibility. (#34182)

[mono][llvm] Improve LLVM 9 compatibility. (#34182)

Improve LLVM 9 compatibility.

Several intrinsics were removed in LLVM 7 and above; replace them with
IR sequences that generate the desired instructions.

Fix some type mismatch problems with the generated IR (in
Sse2.StoreAlignedNonTemporal, Vector128.CreateScalarUnsafe, and
Sse2.MaskMove); these were caught by running the coreclr hardware
intrinsic JIT tests.

Support the two-argument forms of Sse.SqrtScalar, Sse.ReciprocalScalar,
and Sse.ReciprocalSqrtScalar.

llvm::linkCoreCLRGC(), in llvm/CodeGen/GCs.h, was removed and replaced with
llvm::linkAllBuiltinGCs(), in llvm/CodeGen/BuiltinGCs.h.

In mono_llvm_dump_value and mono_llvm_dump_module, flush the c library's
stdout stream before using (and flushing) LLVM's own buffered output
functions.