Reland "Reland "Reland "Reland "[X86][RFC] Enable `_Float16` type support on...

Reland "Reland "Reland "Reland "[X86][RFC] Enable `_Float16` type support on X86 following the psABI""""

This resolves problems reported in commit 1a202529.
1. Promote to float lowering for nodes XINT_TO_FP
2. Bail out f16 from shuffle combine due to vector type is not legal in the version