Bump Go version to 1.23.6 (#30242)

* Bump Go version to 1.23.6

* Update CodeQL Github action as well

* Use server's Go version for CodeQL action

Co-authored-by: Antonis Stamatiou <stamatiou.antonis@gmail.com>

* Empty commit to trigger CI

* Bump golangci-lint to a version supporting Go 1.23

* Fix golangci-lint warnings

Several rules from gosimple, revive and staticcheck linters were
failing:
- Redefinition of built-in identifiers (max, min, new, recover...)
- Use of printf-like functions with simple strings
- Check for nil slices, when len already takes it into account

---------

Co-authored-by: Antonis Stamatiou <stamatiou.antonis@gmail.com>
Co-authored-by: Mattermost Build <build@mattermost.com>

server/channels/app/server.go

@@ -463,9 +463,9 @@ func NewServer(options ...Option) (*Server, error) {
 		return s, nil
 	}
 
-	s.platform.AddConfigListener(func(old, new *model.Config) {
+	s.platform.AddConfigListener(func(oldCfg, newCfg *model.Config) {
 		appInstance := New(ServerConnector(s.Channels()))
-		if *old.GuestAccountsSettings.Enable && !*new.GuestAccountsSettings.Enable {
+		if *oldCfg.GuestAccountsSettings.Enable && !*newCfg.GuestAccountsSettings.Enable {
 			c := request.EmptyContext(s.Log())
 			if appErr := appInstance.DeactivateGuests(c); appErr != nil {
 				mlog.Error("Unable to deactivate guest accounts", mlog.Err(appErr))