Guid: optimize comparison functions

[pixelherodev]

guid.Equal() is slow. We call it in a hot loop, and it shows up as a significant part of the profile for one component.

Added benchmarking, and tested a few different approaches. Was reminded by a coworker that == is valid for arrays in Go, and the compiler does a great job:

noam@sylphrena ~/pingthings/goapi/sttp/guid $ go test -bench .
goos: linux
goarch: amd64
pkg: github.com/sttp/goapi/sttp/guid
cpu: AMD Ryzen 9 7900X3D 12-Core Processor          
BenchmarkEqualityIndirect-24            	1000000000	        0.7779 ns/op
BenchmarkEqualityIndirectBaseline-24    	152718645	        7.887 ns/op
BenchmarkEqualityBaseline-24            	179326930	        6.897 ns/op
BenchmarkEqualityCurrent-24             	1000000000	        0.1949 ns/op
BenchmarkEqualityDirect-24              	1000000000	        0.1936 ns/op
PASS
ok  	github.com/sttp/goapi/sttp/guid	5.221s

The current approach has two problems:

• First, the for loop approach is slow. It's hypothetically optimizable, but a == b works just fine for Guids and is ~35x faster.
• Secondly, the indirection, while theoretically inlinable, is not being inlined. With the for loop, it adds 1ns/op - from 6.9 to 7.9 - but with the a == b approach, it adds 0.6ns - from 0.2 to 0.8ns.

Fixing both improves overall throughput from 8ns/op to 0.2ns/op, a ~40x improvement.

I fixed both APIs rather than remove one just so there's no breakage and it's easier to get reviewed.