[PLAT-11040] Support Webpack 5

[gingerbenw]

Goal

Export separate clients from /main and /renderer to allow smaller bundles and support webpack 5 without providing polyfills

Outstanding:

• Re-instate failing windows tests

Design

Create a specific main and renderer process client, rather than detecting the process and creating one or the other.

Changeset

Update test fixture to use latest version of electron-forge and test up to electron v30
Update test assertions to match bundle changes from latest version of electron-forge

Testing

Skipped 2 failing tests which require further investigation

[github-actions]

@bugsnag/browser bundle size diff

	Minified	Minfied + Gzipped
Before	43.80 kB	13.43 kB
After	43.80 kB	13.43 kB
±	No change	No change

code coverage diff

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Generated by 🚫 dangerJS against 6f0bce1

[lemnik]

LGTM - Exciting stuff!