buttons in infobars, "pressed" state

[Caolán McNamara]

tdf#97926 (9e3ba7c3036c4d21e01d6f75ed29a1e8c4208141) added a uno api
to insert infobars with optional buttons which can dispatch commands.

much earlier commits ca36bcc05d7159fd4cd8e3489fdf4b4551b696d6 and
b34eab5996c52269360d166815ef15a250627c48 added features that when
a button is associated with a command then that the button is disabled
if the command is disabled and shown pressed if the associated
FeatureStateEvent has a bool state.

I'm exploring using native buttons in the infobar and the pressed-state
is problematic for me, "toggle" buttons can be set in a pressed state,
but "normal" buttons typically not. Do we know if it is an expected
feature of a button in an infobar that it should be down depressed in
some circumstance, and if it is, is there an example of a command which
has a bool state. Trying some things like .uno:SpellOnline or .uno:Bold
which look sort of toggleable just show void for rEvent.State in
PushButton::statusChanged