KVM: selftests: Add a forced emulation variation of KVM_ASM_SAFE()

Add KVM_ASM_SAFE_FEP() to allow forcing emulation on an instruction that
might fault.  Note, KVM skips RIP past the FEP prefix before injecting an
exception, i.e. the fixup needs to be on the instruction itself.  Do not
check for FEP support, that is firmly the responsibility of whatever code
wants to use KVM_ASM_SAFE_FEP().

Sadly, chaining variadic arguments that contain commas doesn't work, thus
the unfortunate amount of copy+paste.

Tested-by: Dapeng Mi <dapeng1.mi@linux.intel.com>
Link: https://lore.kernel.org/r/20240109230250.424295-28-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>