Draft: DO NOT MERGE: Side-effects-free vue file modules

What does this MR do and why?

Adds tree-shake-ability to side-effect free .vue files.

Some of our files still have side-effects, so we exclude them from tree shaking.

To get the list of .vue files with side-effects — we add a eslint rule to forbid top-level side-effects and export the list of files that violate that. Then we use that list in the webpack config.

Webpack docs on tree shaking: https://webpack.js.org/configuration/module/#rulesideeffects

References

Screenshots or screen recordings

N/A

How to set up and validate locally

TBD

Q: how to run production-like webpack locally?

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