fix(coverage): istanbul provider to work with JSDOM and process.env usage

[AriPerkkio]

Description

• Fixes Error when using process.env.NODE_ENV with jsdom and @vitest/coverage-istanbul #3860

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[AriPerkkio]

Vite has a guide for these cases: https://vitejs.dev/guide/env-and-mode.html#production-replacement

For JavaScript strings, you can break the string up with a Unicode zero-width space, e.g. 'import.meta\u200b.env.MODE'.

Instead of replacing the process.env back and forth, should we just replace them to process\u200b.env and leave that way?

This PR is now verifying that Node specific process.env works when using web transforms.
Are there any web related stuff that gets transformed when running in Node?

[sheremet-va]

I feel like we need a more general solution. process.env.NODE_ENV is replaced even when we don't need it to be (#3933). Maybe we can hijack the internal Vite plugin to not replace it? The plugin is here: https://github.com/vitejs/vite/blob/main/packages/vite/src/node/plugins/clientInjections.ts

[sheremet-va]

I feel like we need a more general solution. process.env.NODE_ENV is replaced even when we don't need it to be (#3933). Maybe we can hijack the internal Vite plugin to not replace it? The plugin is here: vitejs/vite@main/packages/vite/src/node/plugins/clientInjections.ts

Implemented it here: #3957

[AriPerkkio]

#3957 looks a lot more reliable than this one. I'll convert this into test(coverage): JSDOM + process.env usage later.

[AriPerkkio]

Browser tests are still failing with SyntaxError: Unexpected identifier 'test'

[sheremet-va]

Browser tests are still failing with SyntaxError: Unexpected identifier 'test'

Interesting. Browser has a separate server so it's not affected by hijacking (and shouldn't be). process.env.NODE_ENV should be transformed there

[AriPerkkio]

process.env.NODE_ENV should be transformed there

Yes, it is transformed and it breaks the inline source maps where process.env.NODE_ENV is used inside a string.

Any ideas how this should be handled in browser environment?