Rollup merge of #120965 - ChrisDenton:sahf, r=michaelwoerister

Add lahfsahf and prfchw target feature

This adds target features for LAHF/SAHF and PrefetchW. These came up. along with the existing CMPXCHG16b. as [baseline features](https://download.microsoft.com/download/c/1/5/c150e1ca-4a55-4a7e-94c5-bfc8c2e785c5/Windows%2010%20Minimum%20Hardware%20Requirements.pdf) required for x86_64 Windows 10+.