fix(ssr): pretty print plugin error in ssrLoadModule

[hi-ogawa]

Description

• Related Feature request: friendlier error for empty bracket pair in template instead of full js_parse_error being thrown. sveltejs/vite-plugin-svelte#1069

Though this might look like a regression from the before/after screenshots below, this error was never pretty-printed. What's happening in sveltekit's repro is that, a plugin error of ssrLoadModule entry transform was outside this try/catch, so sveltekit were able to try/catch and pretty print on their own with "Internal server error" on Vite 5. Since Vite 6, entry level transform also goes through runner, so any plugin error will be caught through "Error when evaluating SSR module" message.

Currently this automatic logging is fairly verbose and no error pretty printing. I'm not sure what to do with an extra runnerError (maybe make it non-enumerable?), but for now, doing pretty print probably helps the situation a bit and that's what I did it in this PR.

Screenshots

before (vite 5)

https://www.sveltelab.dev/wwj9l72l4etmdhg

before (vite 6)

https://www.sveltelab.dev/o2e6wq4d900igtk

after (this pr)

https://www.sveltelab.dev/r04dodmlt1ekx5n

[pkg-pr-new]

Open in Stackblitz

npm i https://pkg.pr.new/vite@19290

commit: 0c819f7

[sapphi-red]

The change makes sense to me. I'm not sure what to do with the runnerError. Ideally I think we should hide them if the error is expected (e.g. the code includes incorrect syntax).