Implement new, explicit player stances for owners, allies and spectators.

[GraionDilach]

This PR is aimed towards Next+1, it's heavily WIP, it's opened this early to ensure necessary discussion. and to made sure that it gets merged early in a release cycle.

This PR aims to resolve a long-standing issue with stances can't distinguishing between owners and allies.

At this point i only tested the first 5 minutes in the RA mod but I'm fixing issues on the get-go.

Related to #10892, #11093, #11102 and probably a lot more.

[pchote]

As mentioned in IRC it would make the logic a lot cleaner if we could rename StrictAlly back to Ally and then either introduce an explicit OwnerOrAlly stance, or, better, explicitly reference Stance.Owner | Stance.Ally in code / Owner, Ally in yaml.

The update rule should be relatively straightforward, refer to DefineSoundDefaults for an example where we list field on traits to look for, but then instead of maintaining a list of things to report for manual updates you just need to parse the .Value<Stance>(), update the value, and then replace it on the node.

You can define the following helper in UpdateExtensions to make that last step easier:

public static void ReplaceValue(this MiniYamlNode node, object value)
{
	node.Value.Value = FieldSaver.FormatValue(value);
}

[pchote]

stance.HasFlag(Stance.Ally)

[GraionDilach]

Doesn't work on composite flag values.

[pchote]

stance.HasStance(Stance.Ally)

[GraionDilach]

Do note that I am also adding the spectator stance within this PR as well.

I will look into reconsidering Ally to be allies only but that increases a lot of complexity, something I'm not very fond of at this point. My longterm goal with this is to shift all if (player == RenderPlayer) checks to stance lookups anyway.

[pchote]

Moving to the Future milestone so we don't lose this.

[GraionDilach]

I'll probably get to return to this during the weekend, however without actual progress on the reviewing queue I don't see the point of trying to finish this - it would be just wasted effort considering that this'll grow up to be a high-risk high-reward PR ultimately with all the upgrade rules and trait default updates it'll bring to - and my other PRs already are roadblocks on my personal tasklist - #15014 in particular.

[ghost]

:(