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

app/app_test.go

@@ -405,7 +405,7 @@ func TestDoAdvancedPermissionsMigration(t *testing.T) {
 
 	th.App.DoAdvancedPermissionsMigration()
 
-	config := th.App.GetConfig()
+	config := th.App.Config()
 	assert.Equal(t, -1, *config.ServiceSettings.PostEditTimeLimit)
 
 	th.ResetRoleMigration()
@@ -416,7 +416,7 @@ func TestDoAdvancedPermissionsMigration(t *testing.T) {
 	})
 
 	th.App.DoAdvancedPermissionsMigration()
-	config = th.App.GetConfig()
+	config = th.App.Config()
 	assert.Equal(t, 300, *config.ServiceSettings.PostEditTimeLimit)
 }