Pinned New Version of snowflake-sqlalchemy Supporting SQLAlchemy 2

[MinuraPunchihewa]

Description

This PR pins the new release of snowflake-sqlalchemy that supports SQLAlchemy 2. Here is the relevant reference: snowflakedb/snowflake-sqlalchemy#380

In relation to this change, the following has also been done:

1. A previously added tip to install Git (when using Docker) in order to support the use of the forked repository for the above package has been removed from the documentation and the README.
2. The imports in the handler have been re-organized to prevent a circular dependency issue.

Fixes #9024

Type of change

• 🐛 Bug fix (non-breaking change which fixes an issue)

Verification Process

To ensure the changes are working as expected:

• Test Location: tests/unit/handlers/test_snowflake.py for unit tests and mindsdb/integrations/handlers/snowflake_handler/tests/test_snowflake_handler.py for integration tests.
• Verification Steps: Run the above test modules (for integration tests, a Snowflake account will be required).

Checklist:

• My code follows the style guidelines(PEP 8) of MindsDB.
• I have appropriately commented on my code, especially in complex areas.
• Necessary documentation updates are either made or tracked in issues.
• Relevant unit and integration tests are updated or added.

[MinuraPunchihewa]

@ZoranPandovski I believe this works, but I was not able to test it by actually connecting to Snowflake because it seems like the free trial that had been granted to the account that we were using has been revoked.