Fix requires of external CommonJS SWC helpers

[devongovett]

Fixes a regression introduced by #8555. Reproduction

The root cause was that due to library mode rewriting SWC helpers for CJS libraries, the dep had a placeholder: https://github.com/parcel-bundler/parcel/blob/v2/packages/transformers/js/core/src/dependency_collector.rs#L124-L125

Then, when we build our dep map, we use the placeholder rather than the original specifier + "esm":

parcel/packages/transformers/js/src/JSTransformer.js

Lines 734 to 736 in 426852f

	dep.meta.placeholder ??
	dep.specifier +
	(dep.specifierType === 'esm' ? dep.specifierType : ''),

But when looking up the dep, we would still append "esm", leading no dep to be found and therefore no symbols replaced later on:

parcel/packages/transformers/js/src/JSTransformer.js

Lines 751 to 755 in 426852f

	let specifierType = '';
	if (kind === 'Import' || kind === 'Export') {
	specifierType = 'esm';
	}
	let dep = deps.get(source + specifierType);

To fix this, I've changed the way this works so we don't append "esm" but instead use a placeholder for CJS deps on the rust side. This fixes the original issue where CJS and ESM imports for the same specifier wouldn't work, without needing additional metadata. To get that to work, I had to add specifiers for external modules to the dev packager so we remap from the placeholder to the original specifier when requiring them.

[parcel-benchmark]

Benchmark Results

Kitchen Sink ✅

Timings

Description	Time	Difference
Cold	1.97s	-33.00ms
Cached	422.00ms	-42.00ms 🚀

Cold Bundles

Bundle	Size	Difference	Time	Difference
dist/legacy/parcel.7cdb0fad.webp	102.94kb	+0.00b	108.00ms	-218.00ms 🚀
dist/legacy/parcel.7cdb0fad.webp	102.94kb	+0.00b	109.00ms	-219.00ms 🚀
dist/modern/parcel.7cdb0fad.webp	102.94kb	+0.00b	108.00ms	-221.00ms 🚀

Cached Bundles

Bundle	Size	Difference	Time	Difference
dist/legacy/parcel.7cdb0fad.webp	102.94kb	+0.00b	326.00ms	+219.00ms ⚠️
dist/legacy/parcel.7cdb0fad.webp	102.94kb	+0.00b	327.00ms	+220.00ms ⚠️
dist/modern/parcel.7cdb0fad.webp	102.94kb	+0.00b	326.00ms	+218.00ms ⚠️

React HackerNews ✅

Timings

Description	Time	Difference
Cold	12.42s	-47.00ms
Cached	530.00ms	+1.00ms

Cold Bundles

No bundle changes detected.

Cached Bundles

No bundle changes detected.

AtlasKit Editor ✅

Timings

Description	Time	Difference
Cold	2.21m	-429.00ms
Cached	2.65s	+17.00ms

Cold Bundles

No bundle changes detected.

Cached Bundles

No bundle changes detected.

Three.js ✅

Timings

Description	Time	Difference
Cold	8.92s	-30.00ms
Cached	325.00ms	+2.00ms

Cold Bundles

No bundle changes detected.

Cached Bundles

No bundle changes detected.

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