genoutput: Accelerate the place_operands function.

genoutput: Accelerate the place_operands function.

With the increase in the number of modes and patterns for some
backend architectures, the place_operands function becomes a
bottleneck int the speed of genoutput, and may even become a
bottleneck int the overall speed of building the GCC project.
This patch aims to accelerate the place_operands function,
the optimizations it includes are:
1. Use a hash table to store operand information,
   improving the lookup time for the first operand.
2. Move mode comparison to the beginning to avoid the scenarios of most strcmp.

I tested the speed improvements for the following backends,
	Improvement Ratio
x86_64	197.9%
aarch64	954.5%
riscv	2578.6%
If the build machine is slow, then this improvement can save a lot of time.

I tested the genoutput output for x86_64/aarch64/riscv backends,
and there was no difference compared to before the optimization,
so this shouldn't introduce any functional issues.

gcc/
	* genoutput.cc (struct operand_data): Add member 'eq_next' to
	point to the next member with the same hash value in the
	hash table.
	(compare_operands): Move the comparison of the mode to the very
	beginning to accelerate the comparison of the two operands.
	(struct operand_data_hasher): New, a class that takes into account
	the necessary elements for comparing the equality of two operands
	in its hash value.
	(operand_data_hasher::hash): New.
	(operand_data_hasher::equal): New.
	(operand_datas): New, hash table of konwn pattern operands.
	(place_operands): Use a hash table instead of traversing the array
	to find the same operand.
	(main): Add initialization of the hash table 'operand_datas'.