RISC-V: Add vsext/vzext C/C++ intrinsic support

RISC-V: Add vsext/vzext C/C++ intrinsic support

gcc/ChangeLog:

	* config/riscv/iterators.md: Add sign_extend/zero_extend.
	* config/riscv/riscv-vector-builtins-bases.cc (class ext): New class.
	(BASE): Ditto.
	* config/riscv/riscv-vector-builtins-bases.h: Add vsext/vzext support.
	* config/riscv/riscv-vector-builtins-functions.def (vsext): New macro
	define.
	(vzext): Ditto.
	* config/riscv/riscv-vector-builtins-shapes.cc (struct alu_def): Adjust
	for vsext/vzext support.
	* config/riscv/riscv-vector-builtins-types.def (DEF_RVV_WEXTI_OPS): New
	macro define.
	(DEF_RVV_QEXTI_OPS): Ditto.
	(DEF_RVV_OEXTI_OPS): Ditto.
	(DEF_RVV_WEXTU_OPS): Ditto.
	(DEF_RVV_QEXTU_OPS): Ditto.
	(DEF_RVV_OEXTU_OPS): Ditto.
	(vint16mf4_t): Ditto.
	(vint16mf2_t): Ditto.
	(vint16m1_t): Ditto.
	(vint16m2_t): Ditto.
	(vint16m4_t): Ditto.
	(vint16m8_t): Ditto.
	(vint32mf2_t): Ditto.
	(vint32m1_t): Ditto.
	(vint32m2_t): Ditto.
	(vint32m4_t): Ditto.
	(vint32m8_t): Ditto.
	(vint64m1_t): Ditto.
	(vint64m2_t): Ditto.
	(vint64m4_t): Ditto.
	(vint64m8_t): Ditto.
	(vuint16mf4_t): Ditto.
	(vuint16mf2_t): Ditto.
	(vuint16m1_t): Ditto.
	(vuint16m2_t): Ditto.
	(vuint16m4_t): Ditto.
	(vuint16m8_t): Ditto.
	(vuint32mf2_t): Ditto.
	(vuint32m1_t): Ditto.
	(vuint32m2_t): Ditto.
	(vuint32m4_t): Ditto.
	(vuint32m8_t): Ditto.
	(vuint64m1_t): Ditto.
	(vuint64m2_t): Ditto.
	(vuint64m4_t): Ditto.
	(vuint64m8_t): Ditto.
	* config/riscv/riscv-vector-builtins.cc (DEF_RVV_WEXTI_OPS): Ditto.
	(DEF_RVV_QEXTI_OPS): Ditto.
	(DEF_RVV_OEXTI_OPS): Ditto.
	(DEF_RVV_WEXTU_OPS): Ditto.
	(DEF_RVV_QEXTU_OPS): Ditto.
	(DEF_RVV_OEXTU_OPS): Ditto.
	(rvv_arg_type_info::get_base_vector_type): Add sign_exted/zero_extend
	support.
	(rvv_arg_type_info::get_tree_type): Ditto.
	* config/riscv/riscv-vector-builtins.h (enum rvv_base_type): Ditto.
	* config/riscv/vector-iterators.md (z): New attribute.
	* config/riscv/vector.md (@pred_<optab><mode>_vf2): New pattern.
	(@pred_<optab><mode>_vf4): Ditto.
	(@pred_<optab><mode>_vf8): Ditto.