[#6839] Add placed encounter members to combat

[Aioros]

While creating combatants and rolling initiative for placed members is fairly straightforward, I think the main point of contention on the feature would be how to present the option and where it is actually stored. I opted for a client-setting-backed little dialog, shown right before the actual placement of the encounter members.

Closes #6839

[arbron]

I'd probably try to avoid the dialog solution if possible, instead having a setting in the Combat Settings config for what to do when placing actors from an encounter: "Add to Combat", "Add to Combat & Roll Initiative", "Do Nothing".

If there isn't already an existing combat, then nothing would happen.

[Aioros]

The dialog was basically a personal preference coming from the way I imagined myself using the feature. I reasoned that if I had multiple encounters, and only wanted the combatants to be created for some of them, switching the setting back and forth would have felt more cumbersome, while this allows me to decide on the fly, and remember the last choice. I do trust your opinion more though, so let me prepare a different version.

If there isn't already an existing combat, then nothing would happen.

Not sure about this part, I thought creating the combat if it doesn't exist already was kind of a given. Any reason why that would be undesirable?

[Aioros]

The updated branch uses a setting as suggested (and it's quite simpler as a result). It still creates the combat if it doesn't already exist, though.