i386: support micro-levels in target{,_clone} attrs [PR101696]

i386: support micro-levels in target{,_clone} attrs [PR101696]

As mentioned in the PR, we do miss supports target micro-architectures
in target and target_clone attribute. While the levels
x86-64 x86-64-v2 x86-64-v3 x86-64-v4 are supported values by -march
option, they are actually only aliases for k8 CPU. That said, they are more
closer to __builtin_cpu_supports function and we decided to implement
it there.

	PR target/101696

gcc/ChangeLog:

	* common/config/i386/cpuinfo.h (cpu_indicator_init): Add support
	for x86-64 micro levels for __builtin_cpu_supports.
	* common/config/i386/i386-cpuinfo.h (enum feature_priority):
	Add priorities for the micro-arch levels.
	(enum processor_features): Add new features.
	* common/config/i386/i386-isas.h: Add micro-arch features.
	* config/i386/i386-builtins.c (get_builtin_code_for_version):
	Support the micro-arch levels by callsing
	__builtin_cpu_supports.
	* doc/extend.texi: Document that the levels are support by
	  __builtin_cpu_supports.

gcc/testsuite/ChangeLog:

	* g++.target/i386/mv30.C: New test.
	* gcc.target/i386/mvc16.c: New test.
	* gcc.target/i386/builtin_target.c (CHECK___builtin_cpu_supports):
	New.

Co-Authored-By: H.J. Lu <hjl.tools@gmail.com>