Use strings.Cut() instead of string.SplitN()

[ash2k]

1. strings.Cut() generates less garbage as it does not allocate the slice to hold parts.
2. Code with strings.Cut() is more readable as it's easier to deal with bool vs int - less branching is usually required, fewer arguments to the function call, simpler semantics. See bytes, strings: add Cut golang/go#46336.

func BenchmarkCut(b *testing.B) {
	const s = "key=val"
	const sep = "="

	var splitSink []string
	var cut1, cut2 string
	var found bool

	b.Run("split", func(b *testing.B) {
		b.ReportAllocs()
		b.ResetTimer()
		for i := 0; i < b.N; i++ {
			splitSink = strings.SplitN(s, sep, 2)
		}
	})
	b.Run("cut", func(b *testing.B) {
		b.ReportAllocs()
		b.ResetTimer()
		for i := 0; i < b.N; i++ {
			cut1, cut2, found = strings.Cut(s, sep)
		}
	})
	_ = splitSink
	_ = cut1
	_ = cut2
	_ = found
}

goos: darwin
goarch: arm64
pkg: go.opentelemetry.io/otel/sdk/trace
BenchmarkCut
BenchmarkCut/split
BenchmarkCut/split-10         	38834322	        28.62 ns/op	      32 B/op	       1 allocs/op
BenchmarkCut/cut
BenchmarkCut/cut-10           	215805100	         5.536 ns/op	       0 B/op	       0 allocs/op
PASS

[codecov]

Codecov Report

Merging #4049 (eee2369) into main (8445f21) will increase coverage by 0.0%.
The diff coverage is 93.1%.

Additional details and impacted files

@@          Coverage Diff          @@
##            main   #4049   +/-   ##
=====================================
  Coverage   83.3%   83.3%           
=====================================
  Files        181     181           
  Lines      13934   13925    -9     
=====================================
- Hits       11614   11610    -4     
+ Misses      2099    2094    -5     
  Partials     221     221           

Impacted Files	Coverage Δ
baggage/baggage.go	99.0% <83.3%> (+1.5%)	⬆️
exporters/otlp/internal/envconfig/envconfig.go	82.8% <100.0%> (ø)
internal/internaltest/text_map_propagator.go	81.8% <100.0%> (ø)
sdk/resource/env.go	94.0% <100.0%> (ø)
sdk/resource/os_release_unix.go	83.0% <100.0%> (ø)
semconv/internal/http.go	100.0% <100.0%> (ø)

... and 2 files with indirect coverage changes

[MrAlias]

Please include some sort of performance benchmarking with this PR to motivate these changes.

[ash2k]

@MrAlias Added benchmark to the description.

[ash2k]

@pellared Thanks. I was not sure how to name those and hoped to get some suggestions during the review.

[pellared]

@pellared Thanks. I was not sure how to name those and hoped to get some suggestions during the review.

👍 Just please add "regular commits" (do not rebase) in future as it makes reviewing diffs a lot easier 😉

[ash2k]

Fixed the conflict. It's ready for merging.

[MrAlias]

We still need another review from a person with a different employer.