aarch64: Simplify sqmovun expander

aarch64: Simplify sqmovun expander

This patch is a no-op as it removes the explicit vec-concat-zero patterns in favour of vczle/vczbe.
This allows us to delete the explicit expander too. Tests are added to ensure the optimisation required
still triggers.

Bootstrapped and tested on aarch64-none-linux-gnu and aarch64_be-none-elf.

gcc/ChangeLog:

	* config/aarch64/aarch64-simd.md (aarch64_sqmovun<mode>_insn_le): Delete.
	(aarch64_sqmovun<mode>_insn_be): Delete.
	(aarch64_sqmovun<mode><vczle><vczbe>): New define_insn.
	(aarch64_sqmovun<mode>): Delete expander.

gcc/testsuite/ChangeLog:

	* gcc.target/aarch64/simd/pr99195_4.c: Add tests for sqmovun.