[fix] enable Vite pre-bundling except for Svelte packages

[benmccann]

This is part of why you can't use any Svelte packages with CJS dependencies (vitejs/vite#3024), which is probably the top issue we encounter using Vite.

We need to exclude Svelte packages due to vitejs/vite#3910. Pnpm users may need to either (1) set pnpm shamefully-hoist=true or (2) install that dependency in package.json so we can import it.

This PR alone doesn't actually fix much due to vitejs/vite#3910. However, it does allow me to make more progress in working on Vite issues because it allows me to use the kit.vite.optimizeDeps options. When optimizeDeps is set to [] then none of the other options work and there's no way to unset that from the config. Since it shouldn't actually be set anyway, let's go ahead and remove it

[changeset-bot]

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Latest commit: 2fc2654

The changes in this PR will be included in the next version bump.

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@sveltejs/kit	Patch

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[dominikg]

as mentioned in sveltejs/vite-plugin-svelte#125 i think this is not something limited to sveltekit and having it in vite-plugin-svelte would make it more useful.

[benmccann]

I'm totally happy to have it live there. I'll go ahead and merge this for now since we'd also want to move ssr.noExternal. When we get the code into vite-plugin-svelte we can remove it from here

[AaronDDM]

@benmccann not sure if the subsequent change you plan on making will fix this but after this PR was merged - I am getting errors like the following during server build time:

vite v2.4.4 building SSR bundle for production...
...index.svelte:5:14: error: Expected "from" but found "{"
    5 │   import type { Application } from "../../types/Application";

And it's because this line was removed:
https://github.com/sveltejs/kit/pull/2137/files#diff-09b70580810ae66bf783d467b3ea4f54cd1ac4cb57532b38b788145e27cc0983L581

Which I assume enabled optimization of deps.

Not sure if anyone else is running into this, but I've manually gone in and re-introduced the entries: [] property and the errors go away.

[benmccann]

See sveltejs/svelte-preprocess#362 (comment) for more details about that issue