focusAll method
focuses all Participants, which means putting them in theirs default
groups.
Implementation
void focusAll() {
for (Participant r in List.from(paneled, growable: false)) {
_putVideoFrom(r, paneled);
}
for (Participant r in List.from(focused, growable: false)) {
_putVideoFrom(r, focused);
}
_ensureCorrectGrouping();
}