aarch64: Add Arm Neoverse V2 support

aarch64: Add Arm Neoverse V2 support

This patch adds -mcpu/-mtune support for the Arm Neoverse V2 core.
This updates the internal references to "demeter", but leaves "demeter" as an
accepted value to -mcpu/-mtune as it appears in the released GCC 12 series.

Bootstrapped and tested on aarch64-none-linux-gnu.

gcc/ChangeLog:

	* config/aarch64/aarch64-cores.def (neoverse-v2): New entry.
	(demeter): Update tunings to neoversev2.
	* config/aarch64/aarch64-tune.md: Regenerate.
	* config/aarch64/aarch64.cc (demeter_addrcost_table): Rename to
	neoversev2_addrcost_table.
	(demeter_regmove_cost): Rename to neoversev2_addrcost_table.
	(demeter_advsimd_vector_cost): Rename to neoversev2_advsimd_vector_cost.
	(demeter_sve_vector_cost): Rename to neoversev2_sve_vector_cost.
	(demeter_scalar_issue_info): Rename to neoversev2_scalar_issue_info.
	(demeter_advsimd_issue_info): Rename to neoversev2_advsimd_issue_info.
	(demeter_sve_issue_info): Rename to neoversev2_sve_issue_info.
	(demeter_vec_issue_info): Rename to neoversev2_vec_issue_info.
	Update references to above.
	(demeter_vector_cost): Rename to neoversev2_vector_cost.
	(demeter_tunings): Rename to neoversev2_tunings.
	(aarch64_vec_op_count::rename_cycles_per_iter): Use
	neoversev2_sve_issue_info instead of demeter_sve_issue_info.
	* doc/invoke.texi (AArch64 Options): Document neoverse-v2.

(cherry picked from commit 14d4b4fb12041dde1511262b926662929196c3fe)