Add import helper to decrease ESM loader runtime footprint

[mattcompiles]

↪️ Pull Request

While trying to optimize a very large entry bundle, we noticed that the loader runtime was using a lot of bytes via code repetition. This PR adds a new ESM helper that reduces the code footprint of bundle loading.

🚨 Test instructions

Existing tests cover this case and have been updated to reflect the changes.

✔️ PR Todo

• Added/updated unit tests for this change
• Filled out test instructions (In case there aren't any unit tests)
• Included links to related issues/PRs

[parcel-benchmark]

Benchmark Results

Kitchen Sink ✅

Timings

Description	Time	Difference
Cold	2.08s	+55.00ms
Cached	321.00ms	-61.00ms 🚀

Cold Bundles

No bundle changes detected.

Cached Bundles

No bundle changes detected.

React HackerNews ✅

Timings

Description	Time	Difference
Cold	5.51s	-133.00ms
Cached	504.00ms	+15.00ms

Cold Bundles

Bundle	Size	Difference	Time	Difference
dist/PermalinkedComment.b41e2791.js	4.07kb	+0.00b	568.00ms	+96.00ms ⚠️
dist/UserProfile.2a2fa310.js	1.51kb	+0.00b	567.00ms	+94.00ms ⚠️
dist/NotFound.13a965e5.js	399.00b	+0.00b	567.00ms	+94.00ms ⚠️
dist/logo.8dd07848.png	244.00b	+0.00b	437.00ms	+59.00ms ⚠️

Cached Bundles

Bundle	Size	Difference	Time	Difference
dist/index.js	460.80kb	+0.00b	1.23s	-120.00ms 🚀
dist/PermalinkedComment.b41e2791.js	4.07kb	+0.00b	452.00ms	-23.00ms 🚀
dist/UserProfile.2a2fa310.js	1.51kb	+0.00b	452.00ms	-23.00ms 🚀

AtlasKit Editor ✅

Timings

Description	Time	Difference
Cold	52.50s	-690.00ms
Cached	2.72s	-155.00ms 🚀

Cold Bundles

Bundle	Size	Difference	Time	Difference
dist/index.e9c11402.js	3.79mb	-2.22kb 🚀	23.67s	-448.00ms
dist/media-viewer.b0d6ca9e.js	537.60kb	-155.00b 🚀	12.91s	-3.69s 🚀
dist/popup.50441968.js	324.61kb	-13.00b 🚀	17.12s	+462.00ms
dist/ConfigPanelFieldsLoader.a2efc1d2.js	307.31kb	-377.00b 🚀	12.93s	+254.00ms
dist/EmojiPickerComponent.c4802d1e.js	189.88kb	-69.00b 🚀	16.20s	-448.00ms
dist/card.1f42b27b.js	140.38kb	-69.00b 🚀	12.91s	+252.00ms
dist/esm.7d57db8c.js	63.51kb	-26.00b 🚀	17.12s	+462.00ms
dist/esm.0d76f319.js	59.92kb	-69.00b 🚀	12.91s	+243.00ms
dist/component.b6d91d2b.js	57.90kb	+91.00b ⚠️	7.73s	+245.00ms
dist/esm.c23dea85.js	39.62kb	-69.00b 🚀	17.12s	+466.00ms
dist/pdfRenderer.187ba54d.js	12.21kb	+0.00b	12.91s	-3.69s 🚀
dist/ru.896915b9.js	2.94kb	+0.00b	12.91s	+1.14s ⚠️
dist/codeViewerRenderer.f99075be.js	2.74kb	+0.00b	12.91s	-3.69s 🚀
dist/pt_BR.eccfad73.js	2.19kb	+0.00b	9.23s	-2.55s 🚀
dist/heading5.023a8f1f.js	1.36kb	+0.00b	9.22s	+1.36s ⚠️
dist/sk.101f1705.js	786.00b	+0.00b	12.91s	+1.14s ⚠️
dist/pt_PT.402f9c4e.js	765.00b	+0.00b	9.23s	-2.54s 🚀
dist/ro.a6eff34a.js	612.00b	+0.00b	9.23s	-2.54s 🚀
dist/index.html	240.00b	+0.00b	9.24s	+1.84s ⚠️

Cached Bundles

Bundle	Size	Difference	Time	Difference
dist/index.e9c11402.js	3.79mb	-2.22kb 🚀	24.14s	+402.00ms
dist/media-viewer.b0d6ca9e.js	537.60kb	-155.00b 🚀	16.34s	+547.00ms
dist/popup.50441968.js	324.61kb	-13.00b 🚀	16.33s	+548.00ms
dist/ConfigPanelFieldsLoader.a2efc1d2.js	307.31kb	-377.00b 🚀	11.79s	+385.00ms
dist/EmojiPickerComponent.c4802d1e.js	189.88kb	-69.00b 🚀	16.25s	+517.00ms
dist/card.1f42b27b.js	140.38kb	-69.00b 🚀	11.79s	+384.00ms
dist/esm.7d57db8c.js	63.51kb	-26.00b 🚀	16.33s	+548.00ms
dist/esm.0d76f319.js	59.92kb	-69.00b 🚀	11.79s	+386.00ms
dist/component-lazy.1b33c14d.js	59.63kb	+0.00b	7.87s	-775.00ms 🚀
dist/component.b6d91d2b.js	57.90kb	+91.00b ⚠️	7.49s	+57.00ms
dist/esm.c23dea85.js	39.62kb	-69.00b 🚀	16.33s	+543.00ms
dist/pl.5f36d63e.js	2.38kb	+0.00b	8.81s	-2.44s 🚀
dist/ro.a6eff34a.js	612.00b	+0.00b	8.81s	-2.59s 🚀

Three.js ✅

Timings

Description	Time	Difference
Cold	4.29s	+59.00ms
Cached	421.00ms	-0.00ms

Cold Bundles

No bundle changes detected.

Cached Bundles

No bundle changes detected.

Click here to view a detailed benchmark overview.

[marcins]

LGTM.. as you mentioned, it does make the codegen logic a bit more messy with the conditionals, but I don't think that could be avoided without more major changes.