Deprecate proxy parameters and recommend the environment variables

[smtakeda]

Issue description

There are two ways to use proxy server, one of which is by the parameters in connection and other of which is by the environment variables HTTP_PROXY, HTTPS_PROXY and NO_PROXY.

One missing feature by the parameters is NO_PROXY. It is possible to implement gosnowflake own no_proxy, but we want to deprecate the use of parameters as there is no much value to have connection specific proxy. Instead, we recommend to use the environment variables that apply all connections in a process.

A benefit is the environment variables can be shared not only with other Snowflake components (SnowSQL, Python Connector, etc) but also other common tools, e.g., curl.