otellogr: Add benchmarks (#6364)

Add benchmarks (similar to otelslog)
Part of
#5192

Benchmark results:
```
goos: linux
goarch: amd64
pkg: go.opentelemetry.io/contrib/bridges/otellogr
cpu: Intel(R) Core(TM) i9-10885H CPU @ 2.40GHz
BenchmarkLogSink/Info-16                 6114177               186.4 ns/op           160 B/op          1 allocs/op
BenchmarkLogSink/Error-16                6649935               245.2 ns/op           160 B/op          1 allocs/op
BenchmarkLogSink/WithValues-16           3949730               295.6 ns/op           448 B/op          3 allocs/op
BenchmarkLogSink/WithName-16             6813362               172.0 ns/op           133 B/op          2 allocs/op
BenchmarkLogSink/WithName.WithValues-16                  2420191               606.4 ns/op           581 B/op          5 allocs/op
BenchmarkLogSink/(WithName.WithValues).Info-16          12601381                97.32 ns/op            0 B/op          0 allocs/op
PASS
ok      go.opentelemetry.io/contrib/bridges/otellogr    24.125s
```

bridges/otellogr/logsink_test.go

@@ -462,3 +462,92 @@ func TestConvertKVs(t *testing.T) {
 		})
 	}
 }
+
+func BenchmarkLogSink(b *testing.B) {
+	message := "body"
+	keyValues := []any{
+		"string", "hello",
+		"int", 42,
+		"float", 3.14,
+		"bool", false,
+	}
+	err := errors.New("error")
+
+	b.Run("Info", func(b *testing.B) {
+		logSinks := make([]logr.LogSink, b.N)
+		for i := range logSinks {
+			logSinks[i] = NewLogSink("")
+		}
+
+		b.ReportAllocs()
+		b.ResetTimer()
+		for n := 0; n < b.N; n++ {
+			logSinks[n].Info(0, message, keyValues...)
+		}
+	})
+
+	b.Run("Error", func(b *testing.B) {
+		logSinks := make([]logr.LogSink, b.N)
+		for i := range logSinks {
+			logSinks[i] = NewLogSink("")
+		}
+
+		b.ReportAllocs()
+		b.ResetTimer()
+		for n := 0; n < b.N; n++ {
+			logSinks[n].Error(err, message, keyValues...)
+		}
+	})
+
+	b.Run("WithValues", func(b *testing.B) {
+		logSinks := make([]logr.LogSink, b.N)
+		for i := range logSinks {
+			logSinks[i] = NewLogSink("")
+		}
+
+		b.ReportAllocs()
+		b.ResetTimer()
+		for n := 0; n < b.N; n++ {
+			logSinks[n].WithValues(keyValues...)
+		}
+	})
+
+	b.Run("WithName", func(b *testing.B) {
+		logSinks := make([]logr.LogSink, b.N)
+		for i := range logSinks {
+			logSinks[i] = NewLogSink("")
+		}
+
+		b.ReportAllocs()
+		b.ResetTimer()
+		for n := 0; n < b.N; n++ {
+			logSinks[n].WithName("name")
+		}
+	})
+
+	b.Run("WithName.WithValues", func(b *testing.B) {
+		logSinks := make([]logr.LogSink, b.N)
+		for i := range logSinks {
+			logSinks[i] = NewLogSink("")
+		}
+
+		b.ReportAllocs()
+		b.ResetTimer()
+		for n := 0; n < b.N; n++ {
+			logSinks[n].WithName("name").WithValues(keyValues...)
+		}
+	})
+
+	b.Run("(WithName.WithValues).Info", func(b *testing.B) {
+		logSinks := make([]logr.LogSink, b.N)
+		for i := range logSinks {
+			logSinks[i] = NewLogSink("").WithName("name").WithValues(keyValues...)
+		}
+
+		b.ReportAllocs()
+		b.ResetTimer()
+		for n := 0; n < b.N; n++ {
+			logSinks[n].Info(0, message)
+		}
+	})
+}