Add more linters to improve code readability (#19989)

Add nakedret, unconvert, wastedassign, stylecheck and nolintlint linters to improve code readability

- nakedret - https://github.com/alexkohler/nakedret - nakedret is a Go static analysis tool to find naked returns in functions greater than a specified function length.
- unconvert - https://github.com/mdempsky/unconvert - Remove unnecessary type conversions
- wastedassign - https://github.com/sanposhiho/wastedassign -  wastedassign finds wasted assignment statements.
- notlintlint -  Reports ill-formed or insufficient nolint directives
- stylecheck - https://staticcheck.io/docs/checks/#ST - keep style consistent
  - excluded: [ST1003 - Poorly chosen identifier](https://staticcheck.io/docs/checks/#ST1003) and [ST1005 - Incorrectly formatted error string](https://staticcheck.io/docs/checks/#ST1005)

routers/api/v1/activitypub/reqsignature.go

@@ -41,7 +41,7 @@ func getPublicKeyFromResponse(b []byte, keyID *url.URL) (p crypto.PublicKey, err
 		return
 	}
 	p, err = x509.ParsePKIXPublicKey(block.Bytes)
-	return
+	return p, err
 }
 
 func fetch(iri *url.URL) (b []byte, err error) {
@@ -59,7 +59,7 @@ func fetch(iri *url.URL) (b []byte, err error) {
 		return
 	}
 	b, err = io.ReadAll(io.LimitReader(resp.Body, setting.Federation.MaxSize))
-	return
+	return b, err
 }
 
 func verifyHTTPSignatures(ctx *gitea_context.APIContext) (authenticated bool, err error) {
@@ -87,7 +87,7 @@ func verifyHTTPSignatures(ctx *gitea_context.APIContext) (authenticated bool, er
 	// 3. Verify the other actor's key
 	algo := httpsig.Algorithm(setting.Federation.Algorithms[0])
 	authenticated = v.Verify(pubKey, algo) == nil
-	return
+	return authenticated, err
 }
 
 // ReqHTTPSignature function