Feat(events): Allow explicit 0 for events to apply directly

[RisingLeaf]

Feature

This PR addresses the bug/feature described in issue #6719 and as requested by @bene-dictator

Summary

Up til now events were only applied on the next increment of date. This PR allows for an explicit time to event of 0, which mean the event gets applied when the game action is triggered.
Take this example:

event "war begins"
	system Sol
		government "Free Worlds"

mission "Name2"
	job
	repeat
	on accept
		event "war begins" 0

The map changes will be seen as soon as the mission gets accepted

Testing Done

I used the test mission to test it once with explicit 0 and without, worked like expected, with explicit 0 map changes were seen directly, without I had to depart

Performance Impact

N/A

Side Note

I looked through the data files and there is no place where event gets used with a 0, so no need to change anything there.

[TomGoodIdea]

Tested changing map and player swizzle; normal events still work as they should.
Thank you!

[bene-dictator]

The single comment in this PR looks grammatically perfect.

Thank you so much :)

[bene-dictator]

Works as expected with the Hai Start PR.