Make message and broadcast effects accept objects

[TPGamesNL]

Description

Makes EffMessage and EffBroadcast accept objects to broadcast, instead of just strings.
Also makes it so the effects don't call any of the expressions getters multiple times (which is what the ugly code at the start of the second loop in EffMessage#execute is for):

function doStuff() :: text:
	broadcast "func called"
	return "test"

command /test:
	trigger:
		add sender to {_l::*}
		add sender to {_l::*}
		send "Result: %doStuff()%" to {_l::*}

will now only call doStuff once, used to be twice.

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Target Minecraft Versions: any
Requirements: none
Related Issues: #3164

[TPGamesNL]

Now it also fixes the code:

command /test <text>:
	trigger:
		message "text: %coloured arg-1%"

parsing special chat formats (tooltip etc), although this bug was only present on master, not 2.5.3.

It also fixes an exception (SkriptAPIException: Call to getSingle() on a non-single expression) from the code message "text: %coloured ("abc" and "test")%"