fix: prevent cache on optional package resolve

[bluwy]

Description

When resolving optional packages for Vite, like sass, use the resolve package to resolve first to avoid nodejs caching the result (even if the module is not found).

This allows users to install sass while the Vite server is still running, and it'll pick up the changes without restarting.

Additional context

This is tricky to make a test for, but I've confirmed that it's working in the playground projects manually.

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What is the purpose of this pull request?

• Bug fix
• New Feature
• Documentation update
• Other

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[patak-dev]

Interesting hack! I think we should merge this one now and let people test it a bit. @bluwy did you want to backport this one? We could do it if it proves stable in the v4 alpha

[bluwy]

Yep! We could probably check ecosystem-ci when this is released and backport it to v3 when it's good. (I think it'll likely be safe though)