config: rename skip-sql-invoice-migration to skip-native-sql-migration

In future releases we will use this flag to make potentially failing kv
to native SQL migrations optional. For this reason it is better to
rename it to avoid confusion.

lncfg/db.go

@@ -87,7 +87,7 @@ type DB struct {
 
 	UseNativeSQL bool `long:"use-native-sql" description:"Use native SQL for tables that already support it."`
 
-	SkipSQLInvoiceMigration bool `long:"skip-sql-invoice-migration" description:"Do not migrate invoices stored in our key-value database to native SQL."`
+	SkipNativeSQLMigration bool `long:"skip-native-sql-migration" description:"Do not run the KV to native SQL migration. It should only be used if errors are encountered normally."`
 
 	NoGraphCache bool `long:"no-graph-cache" description:"Don't use the in-memory graph cache for path finding. Much slower but uses less RAM. Can only be used with a bolt database backend."`
 
@@ -117,8 +117,8 @@ func DefaultDB() *DB {
 			MaxConnections: defaultSqliteMaxConnections,
 			BusyTimeout:    defaultSqliteBusyTimeout,
 		},
-		UseNativeSQL:            false,
-		SkipSQLInvoiceMigration: false,
+		UseNativeSQL:           false,
+		SkipNativeSQLMigration: false,
 	}
 }