vect: check support for gcond with {cond{_len}_}vec_cbranch_{any|all} optabs [PR118974]

vect: check support for gcond with {cond{_len}_}vec_cbranch_{any|all} optabs [PR118974]

This change allows a target to only implement the explicit vec_cbranch optabs.
To do this the vectorizer is updated to check for the new optabs directly.

Targets that have a different type for BOOLEAN_VECTOR_TYPE_P for instance
can use only the new optabs.

gcc/ChangeLog:

	PR target/118974
	* tree-vect-stmts.cc (supports_vector_compare_and_branch): New.
	(vectorizable_early_exit): Use it.