KVM: VMX: Setup canonical VMCS config prior to kvm_x86_vendor_init()

KVM: VMX: Setup canonical VMCS config prior to kvm_x86_vendor_init()

Setup the golden VMCS config during vmx_init(), before the call to
kvm_x86_vendor_init(), instead of waiting until the callback to do
hardware setup.  setup_vmcs_config() only touches VMX state, i.e. doesn't
poke anything in kvm.ko, and has no runtime dependencies beyond
hv_init_evmcs().

Setting the VMCS config early on will allow referencing VMCS and VMX
capabilities at any point during setup, e.g. to check for PERF_GLOBAL_CTRL
save/load support during mediated PMU initialization.

Tested-by: Xudong Hao <xudong.hao@intel.com>
Link: https://lore.kernel.org/r/20250806195706.1650976-15-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>