KVM: x86: Rework KVM_REQ_MSR_FILTER_CHANGED into a generic RECALC_INTERCEPTS

KVM: x86: Rework KVM_REQ_MSR_FILTER_CHANGED into a generic RECALC_INTERCEPTS

Rework the MSR_FILTER_CHANGED request into a more generic RECALC_INTERCEPTS
request, and expand the responsibilities of vendor code to recalculate all
intercepts that vary based on userspace input, e.g. instruction intercepts
that are tied to guest CPUID.

Providing a generic recalc request will allow the upcoming mediated PMU
support to trigger a recalc when PMU features, e.g. PERF_CAPABILITIES, are
set by userspace, without having to make multiple calls to/from PMU code.
As a bonus, using a request will effectively coalesce recalcs, e.g. will
reduce the number of recalcs for normal usage from 3+ to 1 (vCPU create,
set CPUID, set PERF_CAPABILITIES (Intel only), set filter).

The downside is that MSR filter changes that are done in isolation will do
a small amount of unnecessary work, but that's already a relatively slow
path, and the cost of recalculating instruction intercepts is negligible.

Tested-by: Xudong Hao <xudong.hao@intel.com>
Link: https://lore.kernel.org/r/20250806195706.1650976-25-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>