Fix SqliteHook compatibility with SQLAlchemy engine (#23790)

Same as #19508 but for Sqlite as described in https://docs.sqlalchemy.org/en/14/dialects/sqlite.html#connect-strings to be able to create a Sqlalchemy engine from the URI itself.

Without this, it currently fails with the following error due to how we create URI in Connections. An absolute path is denoted by starting with a slash, means you need four slashes:

```
url = sqlite://%2Ftmp%2Fsqlite.db

    def create_connect_args(self, url):
        if url.username or url.password or url.host or url.port:
>           raise exc.ArgumentError(
                "Invalid SQLite URL: %s\n"
                "Valid SQLite URL forms are:\n"
                " sqlite:///:memory: (or, sqlite://)\n"
                " sqlite:///relative/path/to/file.db\n"
                " sqlite:////absolute/path/to/file.db" % (url,)
            )
E           sqlalchemy.exc.ArgumentError: Invalid SQLite URL: sqlite://%2Ftmp%2Fsqlite.db
E           Valid SQLite URL forms are:
E            sqlite:///:memory: (or, sqlite://)
E            sqlite:///relative/path/to/file.db
E            sqlite:////absolute/path/to/file.db
```

airflow/providers/sqlite/hooks/sqlite.py

@@ -36,6 +36,12 @@ def get_conn(self) -> sqlite3.dbapi2.Connection:
         conn = sqlite3.connect(airflow_conn.host)
         return conn
 
+    def get_uri(self) -> str:
+        """Override DbApiHook get_uri method for get_sqlalchemy_engine()"""
+        conn_id = getattr(self, self.conn_name_attr)
+        airflow_conn = self.get_connection(conn_id)
+        return f"sqlite:///{airflow_conn.host}"
+
     @staticmethod
     def _generate_insert_sql(table, values, target_fields, replace, **kwargs):
         """

tests/providers/sqlite/hooks/test_sqlite.py

@@ -21,6 +21,8 @@
 from unittest import mock
 from unittest.mock import patch
 
+import sqlalchemy
+
 from airflow.models import Connection
 from airflow.providers.sqlite.hooks.sqlite import SqliteHook
 
@@ -126,3 +128,13 @@ def test_generate_insert_sql_replace_true(self):
         )
 
         assert sql == expected_sql
+
+    def test_sqlalchemy_engine(self):
+        """Test that the sqlalchemy engine is initialized"""
+        conn_id = 'sqlite_default'
+        hook = SqliteHook(sqlite_conn_id=conn_id)
+        engine = hook.get_sqlalchemy_engine()
+        assert isinstance(engine, sqlalchemy.engine.Engine)
+        assert engine.name == 'sqlite'
+        # Assert filepath of the sqliate DB is correct
+        assert engine.url.database == hook.get_connection(conn_id).host