SNOW-3121122: Meta: Support for SQLAlchemy 2.1

[Dev-iL]

What is the current behavior?

snowflake-sqlalchemy cannot be imported when SQLAlchemy 2.1.0b1 is installed. Example issue:

>>> from snowflake import sqlalchemy 
Traceback (most recent call last):
  File "<python-input-0>", line 1, in <module>
    from snowflake import sqlalchemy
  File "/home/USER/repositories/snowflake-sqlalchemy/src/snowflake/sqlalchemy/__init__.py", line 30, in <module>
    from . import base, snowdialect  # noqa
    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/USER/repositories/snowflake-sqlalchemy/src/snowflake/sqlalchemy/base.py", line 240, in <module>
    class SnowflakeORMSelectCompileState(context.ORMSelectCompileState):
                                         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
AttributeError: module 'sqlalchemy.orm.context' has no attribute 'ORMSelectCompileState'

What is the desired behavior?

• Short term - ability to import snowflake-sqlalchemy when SQLAlchemy 2.1 is installed.
• Long term - full support for SQLAlchemy 2.1.

How would this improve snowflake-connector-python?

Better flexibility for integration with other tools.

References, Other Background

• Related: Snowflake's continued commitment to SQLAlchemy #635
• Compatibility with SQLA2.1 apache/airflow#61229
• Example Airflow CI failure