feat(auth): Allow global config to be located in XDG directory

[elramen]

If the global config file does not exist in the home directory, look in the following paths:

• Linux: $XDG_CONFIG_HOME/sentry/sentrycli.ini and $HOME/.config/sentry/sentrycli.ini
• Mac: $HOME/Library/Application Support/sentry/sentrycli.ini
• Windows: {FOLDERID_RoamingAppData}

This enables users to keep their home dir clean, adhering to standards such as XDG on linux.

Fixes GH-1521