Allow to set multiple keys to use for a host

[CubicrootXYZ]

Is your feature request related to a problem? Please describe.

When having 2 keys in use that both need on demand unlocking (e.g. 2 yubikeys) I can not use both without changing the settings.

In the hosts settings I can switch between:

1. Using yubikey 1 => yubikey 2 fails with Your host doesn't support 'password' or 'keyboard-interactive' authentication
2. Using yubikey 2 => yubikey 1 fails with Your host doesn't support 'password' or 'keyboard-interactive' authentication
3. Use any unlocked key => yubikey will not get unlocked, fails with unauthenticated
4. Use no key => need one

Describe the solution you'd like

An option to select multiple keys to be used for a host or at least an option to unlock any key on connecting.

Describe alternatives you've considered

Leaving as is => requires switching the config any time I want to use the other yubikey.