Improve serverEntrypoint codegen

[bluwy]

Changes

Remove vitePluginFileURL as it's now builtin to Vite 6. Also updated renderer.serverEntrypoint code generation to be more robust. I've found these improvements from debugging #12556, but it does not fix it yet. I'll send a separate PR in Vite to fix that issue instead.

Testing

Existing tests should pass

Docs

n/a. refactors.

[changeset-bot]

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Latest commit: 4af81d4

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[ascorbic]

Looks like there's another here

[codspeed-hq]

CodSpeed Performance Report

Merging #12566 will not alter performance

_{Comparing remove-fileurl-handling (4af81d4) with main (c50882d)}

Summary

✅ 6 untouched benchmarks

[bluwy]

Looks like removing the fileurl handling caused other issues. Gonna revert that for now and fix the codegen stuff only.