Feat/2976 snowpark container auth

[mohamedmeqlad99]

Description

Added support for automatic OAuth token authentication when running inside Snowpark Container Services. This change enables dlt to:

• Auto-detect OAuth token from /snowflake/session/token
• Use SNOWFLAKE_HOST and SNOWFLAKE_ACCOUNT environment variables
• Support token-based auth without requiring username
• Maintain backward compatibility with existing auth methods

Changes include:

• Updated SnowflakeCredentials class
• Added comprehensive test coverage
• Updated Snowflake configuration documentation

Related Issues

• Closes Support Snowflake-provided OAuth token in Snowpark Container Services #2976

Additional Context

Testing:

• Added unit tests in test_snowflake_snowpark_token.py
• Verified auto-detection works as expected
• Confirmed explicit credentials take precedence
• Validated connector parameter generation

Documentation:

• Added new section for Snowpark Container Services auth
• Included usage examples and override instructions

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[burnash]

Thanks for the PR @mohamedmeqlad99 please address the comment below. To use the token-only auth you'd need to actually actively probe for the type of token, e.g. (os.path.exists("/snowflake/session/token")) see https://docs.snowflake.com/en/developer-guide/snowpark-container-services/additional-considerations-services-jobs#connecting-with-a-snowflake-provided-oauth-token

Also please fix linting to ensure the our CI pass. Run make lint to see where it fails.

[burnash]

This may break other oauth flows https://docs.snowflake.com/en/developer-guide/python-connector/python-connector-connect#connecting-with-oauth where user is actually required.