Normalize code frames on thrown errors so that code always exists

[Aaronius]

🙋 feature request

When using the Parcel API and an error is thrown, there's no guarantee that error.diagnostics.*.codeFrame.code exists. If it doesn't then the consumer of the API has to duplicate this logic to retrieve the code pertaining to the code frame:

parcel/packages/core/utils/src/prettyDiagnostic.js

Lines 52 to 55 in c4e494f

	let code =
	codeFrame.code ??
	(options &&
	(await options.inputFS.readFile(nullthrows(filePath), 'utf8')));

This is kind of a pain. I would love to see Parcel normalize these errors so that when a consumer receives a code frame on an error, the code property always exists and the consumer doesn't have to bother with reading source files directly.

🤔 Expected Behavior

I would expect the code property to always exists on any code frame being reported by Parcel.

😯 Current Behavior

The code property only sometimes exists on a code frame.

💁 Possible Solution

If a plugin doesn't provide the code property, Parcel could add it before the error makes its way to the Parcel consumer.

🔦 Context

This is described in further detail in #5081.

💻 Examples

[mischnic]

to the Parcel consumer

That is: reporters and the BuildError thrown when using the API

[hiteshvijayhv]

I would like to claim this issue

[DeMoorJasper]

Sure, feel free to take this.

Interested in what the performance impacts for this would be.