Support temporary AWS credentials for Redshift and Snowflake S3 imports

[Halama]

Temporary AWS credentials provided STS service should be support by Redshift and Snowflake implementation. This means optional AWS_TOKEN parameter should be accepted.

• Snowflake - https://docs.snowflake.net/manuals/sql-reference/sql/copy-into-location.html#additional-cloud-provider-parameters
• Redshift - https://docs.aws.amazon.com/redshift/latest/dg/copy-parameters-authorization.html#copy-access-key-id

Required by https://github.com/keboola/connection/issues/1783