tree - support custom payload when selecting, focusing etc

[jrieken]

blocks #64727

The outline depends on sending payloads when setting focus or selection. This prevent infinite event handling et al. The new tree doesn't support that, it only support an UIEvent

[joaomoreno]

#64743

Can you maybe elaborate on why this is exactly needed, on the other issue? I have a feeling we can do without it: that the fact that there is a browserEvent at all or not is sufficient to prevent these loops.