Optimize V16QI/V32QI/V64QI shift by constant.

Optimize V16QI/V32QI/V64QI shift by constant.

gcc/ChangeLog:
	PR target/95524
	* config/i386/i386-expand.c
	(ix86_expand_vec_shift_qihi_constant): New function.
	* config/i386/i386-protos.h
	(ix86_expand_vec_shift_qihi_constant): Declare.
	* config/i386/sse.md (<shift_insn><mode>3): Optimize shift
	V*QImode by constant.

gcc/testsuite/ChangeLog:
	* gcc.target/i386/avx2-shiftqihi-constant-1.c: New test.
	* gcc.target/i386/avx2-shiftqihi-constant-2.c: Ditto.
	* gcc.target/i386/avx512bw-shiftqihi-constant-1.c: Ditto.
	* gcc.target/i386/avx512bw-shiftqihi-constant-2.c: Ditto.
	* gcc.target/i386/sse2-shiftqihi-constant-1.c: Ditto.
	* gcc.target/i386/sse2-shiftqihi-constant-2.c: Ditto.