Add support for SQLAlchemy 2.0

[rubenwardy]

As an example, sync_trigger gives you the following error:

TypeError: Additional arguments should be named _, got 'autoload'

File "/home/cdb/migrations/versions/2f3c3597c78d_.py", line 27, in upgrade
    sync_trigger(conn, 'package', 'search_vector', ["title", "short_desc", "desc"])
  File "/usr/local/lib/python3.10/site-packages/sqlalchemy_searchable/__init__.py", line 446, in sync_trigger
    table = sa.Table(
  File "<string>", line 2, in __new__
  File "/usr/local/lib/python3.10/site-packages/sqlalchemy/util/deprecations.py", line 277, in warned
    return fn(*args, **kwargs)  # type: ignore[no-any-return]
  File "/usr/local/lib/python3.10/site-packages/sqlalchemy/sql/schema.py", line 428, in __new__
    return cls._new(*args, **kw)
  File "/usr/local/lib/python3.10/site-packages/sqlalchemy/sql/schema.py", line 482, in _new
    with util.safe_reraise():
  File "/usr/local/lib/python3.10/site-packages/sqlalchemy/util/langhelpers.py", line 147, in __exit__
    raise exc_value.with_traceback(exc_tb)
  File "/usr/local/lib/python3.10/site-packages/sqlalchemy/sql/schema.py", line 478, in _new
    table.__init__(name, metadata, *args, _no_init=False, **kw)
  File "/usr/local/lib/python3.10/site-packages/sqlalchemy/sql/schema.py", line 848, in __init__
    self._extra_kwargs(**kw)
  File "/usr/local/lib/python3.10/site-packages/sqlalchemy/sql/schema.py", line 996, in _extra_kwargs
    self._validate_dialect_kwargs(kwargs)
  File "/usr/local/lib/python3.10/site-packages/sqlalchemy/sql/base.py", line 562, in _validate_dialect_kwargs
    raise TypeError(
TypeError: Additional arguments should be named <dialectname>_<argument>, got 'autoload'