slices: change implementation for Clone()

Change the implementation of slices Clone. It's 28% faster on my laptop. As discussed in #57433 (comment), no extra issue is needed for this simple fix.

goos: darwin
goarch: arm64
pkg: github.com/David-Mao/Euclid/Go/utils
         │   old.txt   │               new.txt               │
         │   sec/op    │   sec/op     vs base                │
Clone-12   16.95n ± 1%   12.06n ± 2%  -28.85% (p=0.000 n=10)

src/slices/slices.go

@@ -340,7 +340,9 @@ func Clone[S ~[]E, E any](s S) S {
 	if s == nil {
 		return nil
 	}
-	return append(S([]E{}), s...)
+	t := make([]E, len(s))
+	copy(t, s)
+	return t
 }
 
 // Compact replaces consecutive runs of equal elements with a single copy.