Allow showing messages from threads in Editor Log

[KoBeWi]

Previously if EditorLog received a message from another thread it would get silently ignored. So I changed it to instead use call_deferred(), which AFAIK is safe to use this way.

This PR only affects tool scripts and editor errors, runtime thread errors still don't show (although maybe a similar approach could be used to at least report something). Example code that previously would fail silently:

@tool
extends Node

var thread

func _ready() -> void:
	thread = Thread.new()
	thread.start(test)

func test():
	call("error")

[akien-mga]

Makes sense, though we should make sure we won't trigger situations with infinite feedback loops such as the ones EditorToaster can trigger: #76820.

Would it make sense to defer all messages, even on the main thread?

[KoBeWi]

Makes sense, though we should make sure we won't trigger situations with infinite feedback loops such as the ones EditorToaster can trigger

I think infinite loop is not possible. Also this PR simply makes some warnings/errors that only appeared in the external console to appear in the editor log. I don't recall anything spammy enough to overload the log.

Would it make sense to defer all messages, even on the main thread?

I just modified an existing code that had a special case for other threads; making everything deferred would work too.

[akien-mga]

Thanks!