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/commit_reader.go

@@ -49,9 +49,8 @@ readLoop:
 			if len(line) > 0 && line[0] == ' ' {
 				_, _ = signatureSB.Write(line[1:])
 				continue
-			} else {
-				pgpsig = false
 			}
+			pgpsig = false
 		}
 
 		if !message {