AArch64: Add better costing for vector constants and operations

This patch adds extended costing to cost the creation of constants and the
manipulation of constants.  The default values provided are based on
architectural expectations and each cost models can be individually tweaked as
needed.

The changes in this patch covers:

* Construction of PARALLEL or CONST_VECTOR:
  Adds better costing for vector of constants which is based on the constant
  being created and the instruction that can be used to create it.  i.e. a movi
  is cheaper than a literal load etc.
* Construction of a vector through a vec_dup.

gcc/ChangeLog:

	* config/arm/aarch-common-protos.h (struct vector_cost_table): Add
	movi, dup and extract costing fields.
	* config/aarch64/aarch64-cost-tables.h (qdf24xx_extra_costs,
	thunderx_extra_costs, thunderx2t99_extra_costs,
	thunderx3t110_extra_costs, tsv110_extra_costs, a64fx_extra_costs): Use
	them.
	* config/arm/aarch-cost-tables.h (generic_extra_costs,
	cortexa53_extra_costs, cortexa57_extra_costs, cortexa76_extra_costs,
	exynosm1_extra_costs, xgene1_extra_costs): Likewise
	* config/aarch64/aarch64-simd.md (aarch64_simd_dup<mode>): Add r->w dup.
	* config/aarch64/aarch64.c (aarch64_rtx_costs): Add extra costs.

gcc/testsuite/ChangeLog:

	* gcc.target/aarch64/vect-cse-codegen.c: New test.