MM-14143 config cleanup final (#10374)

* TestGetLicenseFileFromDisk: avoid using fileutils.FindConfigFile

* config: abstract config-related file access, extend memory store

* simplify config validate to avoid file knowledge

* fix relative file tests

* cluster: fix ConfigChanged event

The old and new configurations were swapped when notifying the enterprise code of configuration changes, creating needless instability in propagating config updates across a cluster.

* config/database: ignore duplicates

* test cleanup

* remove unnecessary Save() in test

config/export_test.go

@@ -21,3 +21,8 @@ func UnmarshalConfig(r io.Reader, allowEnvironmentOverrides bool) (*model.Config
 func InitializeConfigurationsTable(db *sqlx.DB) error {
 	return initializeConfigurationsTable(db)
 }
+
+// ResolveConfigFilePath exposes the internal resolveConfigFilePath to test only.
+func ResolveConfigFilePath(path string) (string, error) {
+	return resolveConfigFilePath(path)
+}