MM-13893: refactor config (#10230)

* refactor utils/config* to config/

* pull validateLdapFilter into app

* clean up Config/GetConfig/GetSanitizedConfig usage

Eliminate app.GetConfig() in favour of just using app.Config() directly,
but expose app.GetSanitizedConfig() for when the old behaviour was
required.

* web: isolate config setup

* TestInvitePeopleProvider: make config explicit

* regenerateClientConfig: avoid racey map access

* integrate watch flag into app.ConfigFile option

* make app.Option return an error

* release.mk: only cp static files from config/

* release.mk: fix cp static files from config/

* api4: TestPlugin cleanup

* s/c/cfg/ for clarity

* fix merge conflict

* testlib: allow customization of testlib driver name

api4/post_test.go

@@ -741,7 +741,7 @@ func TestPinPost(t *testing.T) {
 	CheckForbiddenStatus(t, resp)
 
 	t.Run("unable-to-pin-post-in-read-only-town-square", func(t *testing.T) {
-		townSquareIsReadOnly := *th.App.GetConfig().TeamSettings.ExperimentalTownSquareIsReadOnly
+		townSquareIsReadOnly := *th.App.Config().TeamSettings.ExperimentalTownSquareIsReadOnly
 		th.App.SetLicense(model.NewTestLicense())
 		th.App.UpdateConfig(func(cfg *model.Config) { *cfg.TeamSettings.ExperimentalTownSquareIsReadOnly = true })