x86/pmu: Add lib/x86/pmu.[c.h] and move common code to header files

Given all the PMU stuff coming in, we need e.g. lib/x86/pmu.h to hold all
of the hardware-defined stuff, e.g. #defines, accessors, helpers and structs
that are dictated by hardware. This will greatly help with code reuse and
reduce unnecessary vm-exit.

Opportunistically move lbr msrs definition to header processor.h.

Suggested-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Like Xu <likexu@tencent.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Link: https://lore.kernel.org/r/20221102225110.3023543-14-seanjc@google.com