Use a faster method to convert ints to strings

[apocelipes]

"strconv.FormatInt" is faster and does less allocations than "fmt.Sprint". Let's do the right thing with the right tools.

benchmark:

go version 1.23.4

func BenchmarkFmtSprint(b *testing.B) {
	for i := range b.N {
		_ = fmt.Sprint(i)
	}
}

func BenchmarkStrconv(b *testing.B) {
	for i := range b.N {
		strconv.FormatInt(int64(i), 10)
	}
}