feat(backend): organise service dependencies

**Service Dependencies**

Services that depend on other services now access those services via the `Invoker` object. This object is provided to the service as a kwarg to its `start()` method.

Until now, most services did not utilize this feature, and several services required their dependencies to be initialized and passed in on init.

Additionally, _all_ services are now registered as invocation services - including the low-level services. This obviates issues with inter-dependent services we would otherwise experience as we add workflow storage.

**Database Access**

Previously, we were passing in a separate sqlite connection and corresponding lock as args to services in their init. A good amount of posturing was done in each service that uses the db.

These objects, along with the sqlite startup and cleanup logic, is now abstracted into a simple `SqliteDatabase` class. This creates the shared connection and lock objects, enables foreign keys, and provides a `clean()` method to do startup db maintenance.

This is not a service as it's only used by sqlite services.

invokeai/app/services/session_queue/session_queue_sqlite.py

@@ -29,6 +29,7 @@ from invokeai.app.services.session_queue.session_queue_common import (
     calc_session_count,
     prepare_values_to_insert,
 )
+from invokeai.app.services.shared.db import SqliteDatabase
 from invokeai.app.services.shared.models import CursorPaginatedResults
 
 
@@ -45,13 +46,11 @@ class SqliteSessionQueue(SessionQueueBase):
         local_handler.register(event_name=EventServiceBase.queue_event, _func=self._on_session_event)
         self.__invoker.services.logger.info(f"Pruned {prune_result.deleted} finished queue items")
 
-    def __init__(self, conn: sqlite3.Connection, lock: threading.Lock) -> None:
+    def __init__(self, db: SqliteDatabase) -> None:
         super().__init__()
-        self.__conn = conn
-        # Enable row factory to get rows as dictionaries (must be done before making the cursor!)
-        self.__conn.row_factory = sqlite3.Row
+        self.__lock = db.lock
+        self.__conn = db.conn
         self.__cursor = self.__conn.cursor()
-        self.__lock = lock
         self._create_tables()
 
     def _match_event_name(self, event: FastAPIEvent, match_in: list[str]) -> bool: