reapply Presto and Snowflake support enhancements

[sfenner-eb]

Snowflake: Allow auth by PKCS8 key for Snowflake (password auth disabled) User private key specification Mapping bigint to Integer

Presto: Allow verify http session with certificate for Presto Allow using basic authentication for Presto Presto Port specification Presto HTTP scheme specification Presto certificate specification Mapping bigint to Integer

[sfenner-eb]

RE: comment on last PR regarding imports

Shall I update project dependencies for these imports (they are included in Snowflake import for now, but not independently ) from cryptography.hazmat.primitives import serialization from cryptography.hazmat.backends import default_backend

[erezsh]

If we import that dependency (which your PR does), it's better to put the explicitly together with the snowflake connector. And to repeat my previous comment, they need to be imported "on-demand" inside import_snowflake().