LLVM Lands Some Long Overdue Tuning Optimizations For AMD Zen 4

Merged today to the LLVM/Clang compiler codebase are some long overdue adjustments to the AMD Zen 4 "znver4" CPU model for more accurately assessing various latency timings and micro-ops. These values were initially copied over from the Zen 3 (znver3) target but never adjusted properly for Zen 4 until now when an independent contributor took to sorting it out...