fix: minor fixes to get working

[pnadolny13]

• Closes Unexpected error: AttributeError: 'NoneType' object has no attribute 'storage' on prefix = batch_config.storage.prefix or "" #26
• Closes Unexpected error: Object '{schema_name}' already exists during Snowflake CREATE SCHEMA #18
• Closes chore: Upstream breaking changes to SQLConnector - please pin sdk #16

• completes the TODO related to refactor: make DDL overridable for column ADD, ALTER, and RENAME operations meltano/sdk#1114
• Adds a default batch config because its required. Default to writing locally.
• Add copy syntax if key properties dont exist. Previously the merge logic was invalid due to syntax errors. Apparently my first test data didnt have key properties
• conform_record_data_types requires a new level kwarg and was failing because it was missing.
• the column_exists methods was being called a ton and was querying snowflake for all columns every time which was slow so I have it caching now
• the schema_exists method failed for me because get_schema_names returns all lower columns. It errored because it was trying to create a schema that already existed.
• bumped SDK to 0.27.0
• after bumping the SDK I needed to address chore: Upstream breaking changes to SQLConnector - please pin sdk #16 which means create_sqlalchemy_engine was effectively replaced with create_engine
• Also fix import failure of lazy_chunked_generator that was moved in SDK

I'm able to test that this works with the sample tap-github data from the getting started guide.