[MM-47384] Make OpenID Connect free for all (#21556)

* wip: make OpenID Connect free-for-all

* Deprecation note: GoogleOAuth, Office365OAuth

* Improve deprecation comments

Co-authored-by: Martin Kraft <martin@upspin.org>

* Lint fix

* Add model/oauthproviders, move google, openid, office365 from enterprise

* Vet fixes

* Remove redundant log

Co-authored-by: Martin Kraft <martin@upspin.org>
Co-authored-by: Mattermod <mattermod@users.noreply.github.com>

app/user_test.go

@@ -23,7 +23,7 @@ import (
 	"github.com/mattermost/mattermost-server/v6/einterfaces"
 	"github.com/mattermost/mattermost-server/v6/einterfaces/mocks"
 	"github.com/mattermost/mattermost-server/v6/model"
-	oauthgitlab "github.com/mattermost/mattermost-server/v6/model/gitlab"
+	oauthgitlab "github.com/mattermost/mattermost-server/v6/model/oauthproviders/gitlab"
 	"github.com/mattermost/mattermost-server/v6/store"
 	storemocks "github.com/mattermost/mattermost-server/v6/store/storetest/mocks"
 	"github.com/mattermost/mattermost-server/v6/utils/testutils"