RISC-V: Factor out vector manager code in vsetvli insertion pass. [NFC]

RISC-V: Factor out vector manager code in vsetvli insertion pass. [NFC]

gcc/ChangeLog:

	* config/riscv/riscv-vsetvl.cc (pass_vsetvl::get_vector_info):
	New.
	(pass_vsetvl::get_block_info): New.
	(pass_vsetvl::update_vector_info): New.
	(pass_vsetvl::simple_vsetvl): Use get_vector_info.
	(pass_vsetvl::compute_local_backward_infos): Ditto.
	(pass_vsetvl::transfer_before): Ditto.
	(pass_vsetvl::transfer_after): Ditto.
	(pass_vsetvl::emit_local_forward_vsetvls): Ditto.
	(pass_vsetvl::local_eliminate_vsetvl_insn): Ditto.
	(pass_vsetvl::cleanup_insns): Ditto.
	(pass_vsetvl::compute_local_backward_infos): Use
	update_vector_info.