Add default expression to query_expression()

Add default expression to query_expression()

Added a new parameter :paramref:`_orm.query_expression.default_expr` to the
:func:`_orm.query_expression` construct, which will be appled to queries
automatically if the :func:`_orm.with_expression` option is not used. Pull
request courtesy Haoyu Sun.

Fixes: #5198
Closes: #5354
Pull-request: https://github.com/sqlalchemy/sqlalchemy/pull/5354
Pull-request-sha: 57dd4922a3ae4e5fe56dcc541d85ce42256b38b9

Change-Id: I3400f2c00b58bf161f31c74c579feb9ac0f03356
(cherry picked from commit 9be0e9e5477cd6a494d9e3b3c13ceed1e50cc5a9)