Typed dictionary initializer support

[tomfull123]

Allows for the following syntax:

TypedDictionary<int, String> colors = {
	{1, "Red"},
	{2, "Green"}
};

[dsnopek]

Thanks!

This looks just like the equivalent code in Godot, so I'd be inclined to approve it, but there is one difference that I'd like to clear up first

[dsnopek]

I'll bringing up the missing TypedDictionary constructor at today's GDExtension team meeting if Repiteo is there, otherwise I'll ask about it at tomorrow's core team meeting.

Also, like I mentioned on another of your PRs, before this can be merged it needs to get squashed down to a single commit: https://docs.godotengine.org/en/latest/contributing/workflow/pr_workflow.html#the-interactive-rebase

[Repiteo]

Slated for merge on the main repo & this implementation mirrors that nicely

EDIT: Now merged on the main repo!

[tomfull123]

Updated PR to add in changes from godotengine/godot#104664
Unfortunately that includes updating the macro backslashes, which results in a bigger diff

[dsnopek]

Thanks!