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

testlib/helper.go

@@ -40,7 +40,12 @@ func NewMainHelper() *MainHelper {
 
 	utils.TranslationsPreInit()
 
-	settings := storetest.MakeSqlSettings(model.DATABASE_DRIVER_MYSQL)
+	driverName := os.Getenv("MM_SQLSETTINGS_DRIVERNAME")
+	if driverName == "" {
+		driverName = model.DATABASE_DRIVER_MYSQL
+	}
+
+	settings := storetest.MakeSqlSettings(driverName)
 
 	clusterInterface := &FakeClusterInterface{}
 	sqlSupplier := sqlstore.NewSqlSupplier(*settings, nil)