[aarch64] Recursively intialize even and odd sub-parts and merge with zip1.

[aarch64] Recursively intialize even and odd sub-parts and merge with zip1.

gcc/ChangeLog:
	* config/aarch64/aarch64.cc (aarch64_expand_vector_init_fallback): Rename
	aarch64_expand_vector_init to this, and remove 	interleaving case.
	Recursively call aarch64_expand_vector_init_fallback, instead of
	aarch64_expand_vector_init.
	(aarch64_unzip_vector_init): New function.
	(aarch64_expand_vector_init): Likewise.

gcc/testsuite/ChangeLog:
	* gcc.target/aarch64/ldp_stp_16.c (cons2_8_float): Adjust for new
	code-gen.
	* gcc.target/aarch64/sve/acle/general/dupq_5.c: Likewise.
	* gcc.target/aarch64/sve/acle/general/dupq_6.c: Likewise.
	* gcc.target/aarch64/interleave-init-1.c: Rename to ...
	* gcc.target/aarch64/vec-init-18.c: ... this.
	* gcc.target/aarch64/vec-init-19.c: New test.
	* gcc.target/aarch64/vec-init-20.c: Likewise.
	* gcc.target/aarch64/vec-init-21.c: Likewise.
	* gcc.target/aarch64/vec-init-22-size.c: Likewise.
	* gcc.target/aarch64/vec-init-22-speed.c: Likewise.
	* gcc.target/aarch64/vec-init-22.h: New header.