Size regression in `main.js` bundle caused by standalone component migration

[ybnd]

Describe the bug Looks like migrating to standalone components in #2750 increased the size of our main.js bundle by about 30kB.

While this is not a significant increase, it's a bit counter-intuitive since the claim is that standalone components should improve the bundle structure.

Here are some improvements we can make:

• Move route-specific components out of ListableModule and reduce the number of imports
  • Mainly: Standalone Item pages, MyDSpace components
  • This can easily save us ~60kB (gz)
  • A little fragile though: we've already seen that overwriting these components in themes causes regressions. We can propose a workaround to mitigate this.
• Make dynamic form code lazy again
  • Dynamic forms are only used on a select number of routes, many of which are not even accessible by anonymous users, so it would be good to keep them out of the main bundle
  • Looked into this for a short while, and it's not as easy but could save us another ~40kB (gz)