Add support for host env variable or parameter

[LSZ31337]

Idea is to add support for different domains during connection to snowflake backend. Tool always assumes that domain is 'snowflakecomputing.com', unfortunately in case of China it is 'snowflakecomputing.cn', so no connection is possible.

I would like schemachange to respect env value SNOWSQL_HOST or SNOWFLAKE_HOST where I can provide a full url. The same way it is done using 'snowsql'

Thank you