[REQUEST] Parse narrat labels (or script files?) just in time

[liana-p]

Is your feature request related to a problem? Please describe.
(This is pretty low priority as few games even have that problem for the moment).

Large narrat games can take a bit of time to load due to the huge amount of scripts to parse on game load.

We could make this faster by only parsing files or labels when they're reached. It could also save memory by not keeping the data for every single script/label saved constantly. I haven't checked if memory is an issue, but I suspect it could be on large games if played on a lower end device.

Describe the solution you'd like
The game could load all scripts, find all labels (very quick to do), but not parse the actual code in them.

Then only when using a certain label would it parse either the file containing that label, or maybe even just specifically that label, which should pretty much be instant.

Only issue is in dev mode it's useful to parse the whole game on launch to find script issues, so maybe we want an option to still be able to do that during dev, or maybe a "check scripts" button somewhere?

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Additional context
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