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/private/hook_pre_receive.go

@@ -248,7 +248,7 @@ func preReceiveBranch(ctx *preReceiveContext, oldCommitID, newCommitID, refFullN
 	}
 
 	// 5. Check if the doer is allowed to push
-	canPush := false
+	var canPush bool
 	if ctx.opts.DeployKeyID != 0 {
 		canPush = !changedProtectedfiles && protectBranch.CanPush && (!protectBranch.EnableWhitelist || protectBranch.WhitelistDeployKeys)
 	} else {