fix: apply __vitePreload correctly and when necessary

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Description

fixes #19695

This PR fixes:

• vitePreload injection so it doesn't get in the way of Rollup parsing named dynamic imports
• Doesn't apply vitePreload at all if there are no dependencies to load
• Deduplicates the chunk ID -> path mapping across chunks

I've broken this up into smaller PRs and I'm waiting for these to be reviewed and merged first:

• refactor: importAnalysisBuild #19723
• perf: single chunk map #19757

Afterwards:

• Pull in failing test from failing test for #19695 #19721

[privatenumber]

• There's too many changes in here so I'm going to split them up into smaller PRs

[privatenumber]

These imports actually have no side-effects so Rollup should have been tree-shaking them. However, the way the preload method was previously injected prevented them from getting tree-shaken.

Now that it's being applied correctly, Rollup accurately detects that their export values weren't being used, which is why I had to add console.logs here.

[privatenumber]

@bluwy #16184 (review)

Thanks! This looks great to me. Something I'd also like to followup later is to remove the mapDeps altogether if no preloading is needed for the file. Currently it's added unconditionally. And the changes could get a bit big.

This PR accomplishes this.