…s in componentless parent routes

When a componentless parent route has children rendered into a named outlet
(e.g. `outlet: 'inner'`), the `canDeactivate` guard received `null` as the
component argument instead of the actual component instance.

The bug was in `deactivateRouteAndItsChildren`: for componentless routes,
each child was passed the same `context` inherited from the parent lookup,
which was `null` when the parent component only registered a named outlet.
The children's actual outlet contexts were never consulted.

The fix adds a `parentContexts: ChildrenOutletContexts | null` parameter so
that for componentless routes, each child is looked up by its own outlet name
in `parentContexts` (e.g. `parentContexts.getContext('inner')`). For
component routes, `context.children` is passed as the new `parentContexts`
on recursion, ensuring correct context resolution across component boundaries.

This re-addresses angular#34614. A previous fix (angular#36302) was reverted because it
passed `parentContexts` unchanged through component boundaries; this fix
updates `parentContexts` to `context.children` when descending into a
component route, preventing the wrong contexts from propagating into deeper
componentless levels.

Fixes angular#34614