fix: reuse mod.ssrError

[Rich-Harris]

Description

Thank you for the PR to fix vitejs#7030. This addresses my comments in vitejs#7177 (comment) — by storing the error thrown during module instantiation, we can a) save the effort of reinstantiating it, and b) hew closer to the behaviour of browsers and node.

Additional context

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What is the purpose of this pull request?

• Bug fix
• New Feature
• Documentation update
• Other

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[TrickyPi]

Thanks for your professional fix