fix(ssr): encode whitespace in module runner sourceURL

[danielroe]

I hit this testing Nuxt from a directory whose name contains a space. to be fair, I was trying to get errors (testing nuxt/nuxt#36258).

... and lo and behold, I did! any error thrown from a module evaluated by the module runner loses its file name entirely:

Error: boom from utils
    at boom (eval at runInlinedModule (/…/vite/dist/node/module-runner.js:809:9), <anonymous>:6:8)
    at setup (eval at runInlinedModule (...), <anonymous>:12:3)

the same project at a path without a space shows at boom (/.../app/utils/boom.ts:2:9)

V8 only reads the module id up to the first whitespace character (see scanner source), but we previously just wrote the raw module id after //# sourceURL=

this PR percent-encodes just the whitespace when writing the directive, and decodes it back in the two places that turn a frame's file back into a module id (getRunnerSourceMap in the interceptor, and ssrRewriteStacktrace for ssrFixStacktrace).

I decide to encode rather than pathToFileURL because both lookups key off the raw id, and a file:// sourceURL might need a wider id normalisation.

but you may have a different suggestion 🙏