fix: file not found in manifest during build

[gtm-nayan]

fixes #9843

This ensures there is a key for these files in the manifest. Surely there has got to be a better way than this but just leaving it here in case the problems are more widespread and needs a fix overnight. Slightly less efficient than not having these entry points but still beats what we had before.

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[dummdidumm]

You have this in draft mode - does this mean you want to look into a better solution because you know there likely is one, or can we merge the current solution?

[gtm-nayan]

Probably should go ahead with this. Couldn't find any practical way to map the nodes to their chunks. It gets hairier cause parts of a module might end up in different chunks so putting them as entry points seems like the only way for now to guarantee they're in the manifest.

Perhaps @bluwy or @dominikg might know of something. In some rudimentary testing, I found that turning off preserveEntrySignatures gets it down to the same number as without the entrypoints so that could be worth looking into, but later.