feat: emit metrics for command duration and errors

[steved]

We would find it useful to track aggregated metrics outside of the spans emitted.

[rueian]

I did a benchmark to compare WithAttributeSet and WithAttributes.

func BenchmarkWithAttributes(b *testing.B) {
	b.Run("WithAttributeSet", func(b *testing.B) {
		b.ReportAllocs()
		for i := 0; i < b.N; i++ {
			metric.WithAttributeSet(attribute.NewSet(attribute.String("operation", "GET")))
		}
	})
	b.Run("WithAttributes", func(b *testing.B) {
		b.ReportAllocs()
		for i := 0; i < b.N; i++ {
			metric.WithAttributes(attribute.String("operation", "GET"))
		}
	})
}

here is the result:

goarch: arm64
pkg: github.com/redis/rueidis/rueidisotel
cpu: Apple M1 Pro
BenchmarkWithAttributes
BenchmarkWithAttributes/WithAttributeSet
BenchmarkWithAttributes/WithAttributeSet-10         	32767585	        34.79 ns/op	      64 B/op	       1 allocs/op
BenchmarkWithAttributes/WithAttributes
BenchmarkWithAttributes/WithAttributes-10           	14976411	        79.85 ns/op	     144 B/op	       3 allocs/op
PASS

We should avoid WithAttributes.

[rueian]

Thanks @steved !