perf: 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:

func BenchmarkMatch(b *testing.B) {
	for i := 0; i < b.N; i++ {
		if match := indexNameRe.Match([]byte("TestCheckIndexName.index_1")); !match {
			b.Fail()
		}
	}
}

func BenchmarkMatchString(b *testing.B) {
	for i := 0; i < b.N; i++ {
		if match := indexNameRe.MatchString("TestCheckIndexName.index_1"); !match {
			b.Fail()
		}
	}
}

Result:

goos: linux
goarch: amd64
pkg: github.com/zincsearch/zincsearch/pkg/core
cpu: AMD Ryzen 7 PRO 4750U with Radeon Graphics
BenchmarkMatch-16          	 1530795	       776.2 ns/op	      32 B/op	       1 allocs/op
BenchmarkMatchString-16    	 2233713	       591.4 ns/op	       0 B/op	       0 allocs/op
PASS
ok  	github.com/zincsearch/zincsearch/pkg/core	3.799s

[hengfeiyang]

@Juneezee Thanks for the improve.