Extend automation of Volley trait to NPCs

[stwlam]

Closes #7211

Refactored to move common handling of certain traits to a base static class and made the PC version subclass it

[CarlosFdez]

Might need to check for attack roll check type specifically, since you can do athletics checks with weapons (at least not implemented in core, though I think some modules and macros make that possible).

EDIT: agile works with weapons fsr, but not sweep for example

[CarlosFdez]

On second glance, I think the only exception is sweep. The rest seem to be restricted to attacks in general, not just attack rolls, but sweep and finesse specifies attack roll.

[stwlam]

I'm not sure what you mean. These are only used for generating strikes.

[CarlosFdez]

getCheckRollContext() was expanded for all checks was it not?

[CarlosFdez]

Ok no I got, it was expanded to support spell attack rolls, but not all checks (despite its name).

[stwlam]

That's a different PR: #7198