Enable more revive linter rules (#30608)

Noteable additions:

- `redefines-builtin-id` forbid variable names that shadow go builtins
- `empty-lines` remove unnecessary empty lines that `gofumpt` does not
remove for some reason
- `superfluous-else` eliminate more superfluous `else` branches

Rules are also sorted alphabetically and I cleaned up various parts of
`.golangci.yml`.

(cherry picked from commit 74f0c84fa4245a20ce6fb87dac1faf2aeeded2a2)

Conflicts:
	.golangci.yml
	apply the linter recommendations to Forgejo code as well

modules/git/batch_reader.go

@@ -307,10 +307,10 @@ func ParseTreeLine(objectFormat ObjectFormat, rd *bufio.Reader, modeBuf, fnameBu
 
 	// Deal with the binary hash
 	idx = 0
-	len := objectFormat.FullLength() / 2
-	for idx < len {
+	length := objectFormat.FullLength() / 2
+	for idx < length {
 		var read int
-		read, err = rd.Read(shaBuf[idx:len])
+		read, err = rd.Read(shaBuf[idx:length])
 		n += read
 		if err != nil {
 			return mode, fname, sha, n, err