Add vect_recog_popcount_pattern to handle mismatch between the vectorized popcount...

Add vect_recog_popcount_pattern to handle mismatch between the vectorized popcount IFN and scalar popcount builtin.

The patch remove those pro- and demotions when backend support direct
optab.

For i386: it enables vectorization for vpopcntb/vpopcntw and optimized
for vpopcntq.

gcc/ChangeLog:

	PR tree-optimization/97770
	* tree-vect-patterns.c (vect_recog_popcount_pattern):
	New.
	(vect_recog_func vect_vect_recog_func_ptrs): Add new pattern.

gcc/testsuite/ChangeLog:

	PR tree-optimization/97770
	* gcc.target/i386/avx512bitalg-pr97770-1.c: Remove xfail.
	* gcc.target/i386/avx512vpopcntdq-pr97770-1.c: Remove xfail.