chore: teach set module about iter.Seq (#6676)

- Add a new `Seq` function to the `Set` type, this returns an iterator over the values.
- Convert some users of the `Values` method to allow for more optimal code.

Reviewed-on: https://codeberg.org/forgejo/forgejo/pulls/6676
Reviewed-by: Earl Warren <earl-warren@noreply.codeberg.org>
Co-authored-by: Gusted <postmaster@gusted.xyz>
Co-committed-by: Gusted <postmaster@gusted.xyz>

cmd/web.go

@@ -195,7 +195,7 @@ func serveInstalled(ctx *cli.Context) error {
 	publicFilesSet.Remove(".well-known")
 	publicFilesSet.Remove("assets")
 	publicFilesSet.Remove("robots.txt")
-	for _, fn := range publicFilesSet.Values() {
+	for fn := range publicFilesSet.Seq() {
 		log.Error("Found legacy public asset %q in CustomPath. Please move it to %s/public/assets/%s", fn, setting.CustomPath, fn)
 	}
 	if _, err := os.Stat(filepath.Join(setting.CustomPath, "robots.txt")); err == nil {