[X86] Improve pfm counter coverage for llvm-exegesis

This patch attempts to improve pfm perf counter coverage for all the x86 CPUs that libpfm4 supports.

Intel/AMD CPU families tend to share names for cycle/uops counters so even if they don't have a scheduler model yet they can at least use the default values (checked against the libpfm4 source code).

The remaining CPUs (where their port/pipe resource counters are known) I've tried to add to the existing model mappings.

These are untested but don't represent a regression to current llvm-exegesis behaviour for these CPUs.

Differential Revision: https://reviews.llvm.org/D55432

llvm-svn: 348617