Support Authentication via mTLS device certs

Some customers use mTLS device certificates to authenticate Coder CLI and VSCode extension with Coder instead of the Access Token.

Add support for authenticating via mTLS device certs.

We support this already in our VS Code extension.

Start by locating the Windows desktop client's authentication entry points and comparing them with the existing mTLS device-certificate flow in the VS Code extension. Done means Coder CLI and VS Code extension users can authenticate with mTLS device certificates instead of an access token.

索引モデルが issue の本文から書いたものです。