Add monitors without groups info to attributes

[kaystrobach]

The current instance sensor provides these properties:

monitors: 84
monitors_up: 84
monitors_down: 0
monitors_pending: 0
icon: mdi:check-circle-outline

I use groups to organize stuff and display the result on an awtrix 3 clock. Would be awesome to have 4 additional attributes:

no_group_monitors: xx
no_group_monitors_up: xx
no_group_monitors_down: xx
no_group_monitors_pending: xx

These monitors should exclude all monitors of type group from the list. This makes it way easier to create automations, as groups tend to change slower (up to 20secs) than the real monitor. Also groups increase the number of monitors artificially.

Thank you