perf: load dialogs, the SQL console and diff views on first use

- Database dialogs, Assign Shortcut and the Logcat tool window load when shown.
- The SQL console extensions load with the first SQL editor
  (`lazyEditorExtension` reconfigures the editor once they arrive).
- The changes tree loads the diff viewer when a file is selected, and
  "Open Repository Log" loads the revision browser when run.

src/features/database/sqlLanguage.ts

@@ -0,0 +1,2 @@
+/** The language id of SQL files and consoles. */
+export const SQL_LANGUAGE = "sql";