Don't bundle dependencies during build and remove noExternal default

[benmccann]

A large portion of user issues are related to whether packages go in dependencies or devDependencies. This seems to be because of:

kit/packages/create-svelte/templates/default/svelte.config.cjs

Line 17 in 11ec751

noExternal: Object.keys(pkg.dependencies || {})

noExternal means that Vite should bundle the packages. We added this line to have Vite bundle all the dependencies to make deployment to the serverless environments easy. At the moment, in most (if not all) of our adapters, we are using APIs which skip the platform bundling step. However, none of the serverless environments we use actually seem to require this. E.g. Vercel for example can do the bundle themselves using a different file structure. Netlify and Begin also look like they don't require us to bundle in the build step as we're doing today

[benmccann]

#1148 removed noExternal from the template. Though it did not change the way the adapters work. If the adapters still work we can close this. Otherwise, we may need to update them

Even if removing noExternal from the template happened to break the adapters, we should not add it back. Removing it fixed so many issues like #1113 that it needs to remain dead forever