Fixes that a previous commit stopped setting the `example` on the `HeaderLink` which means that its link isn't constructed correctly.

(cherry picked from commit ea7148c)

This change fixes the `updateToV20` schematic which should be a factory function not the schematic itself.

(cherry picked from commit 4052130)

(cherry picked from commit b5fbf52)

See associated pull request for more information.

(cherry picked from commit 464adf0)

We had several places that were optionally injecting `DOCUMENT`, because historically it wasn't guaranteed to be there. That shouldn't be the case anymore so we can clean them up.

(cherry picked from commit a6a385c)

Fixes that we weren't unsubscribing from one observable in the tree.

Fixes #31454.

(cherry picked from commit 69e6600)

The docs are on a separate tsconfig so they didn't have the config that enables type checking of their host bindings.

(cherry picked from commit 933bc24)

Fixes a typo in one of the `theme-color` prompts.

(cherry picked from commit 1bba607)