Add auth options for RemoteRunnable

[kreneskyp]

This PR adds support for most authentication scenarios to RemoteRunnable. It does this by exposing auth kwargs available in the httpx clients.

From the httpx source:

• auth - (optional) An authentication class to use when sending requests.
• headers - (optional) Dictionary of HTTP headers to include when sending requests.
• cookies - (optional) Dictionary of Cookie items to include when sending requests.
• verify - (optional) SSL certificates (a.k.a CA bundle) used to verify the identity of requested hosts. Either True (default CA bundle), a path to an SSL certificate file, an ssl.SSLContext, or False (which will disable verification).
• cert - (optional) An SSL certificate used by the requested host to authenticate the client. Either a path to an SSL certificate file, or two-tuple of (certificate file, key file), or a three-tuple of (certificate file, key file, password).

Testing

• what tests are needed?

[eyurtsev]

@kreneskyp thanks! We're proxying variables here, not super worried about testing this at the moment for the options. Added ability to specify joint client kwargs as well so users can pass either option.