Avoid allocations with (*regexp.Regexp).MatchString

[Juneezee]

We should use (*regexp.Regexp).MatchString instead of (*regexp.Regexp).Match([]byte(...)) when matching string to avoid unnecessary []byte conversions and reduce allocations. A one-line change for free performance improvement.

Example benchmark:

var goTestRegExp = regexp.MustCompile(`_test\.go$`)

func BenchmarkMatch(b *testing.B) {
	for i := 0; i < b.N; i++ {
		if match := goTestRegExp.Match([]byte("file_test.go")); !match {
			b.Fail()
		}
	}
}

func BenchmarkMatchString(b *testing.B) {
	for i := 0; i < b.N; i++ {
		if match := goTestRegExp.MatchString("file_test.go"); !match {
			b.Fail()
		}
	}
}

Result:

goos: linux
goarch: amd64
pkg: github.com/onsi/ginkgo/v2/ginkgo/watch
cpu: AMD Ryzen 7 PRO 4750U with Radeon Graphics
BenchmarkMatch-16          	 5665784	       314.4 ns/op	      16 B/op	       1 allocs/op
BenchmarkMatchString-16    	 8481872	       140.5 ns/op	       0 B/op	       0 allocs/op
PASS
ok  	github.com/onsi/ginkgo/v2/ginkgo/watch	4.321s

[onsi]

SGTM thanks!