Handle application info change for system context

When handling application info changes, we update the application infos
of all the tracked packages. However, we also have the system package,
which is not directly tracked, and thus not updated in this case.

The system context (corresponding to the system package) does not have a
base resources path initially, and it won't have one set, as it is not
updated with the new application info. However, while handling
application info changes, we also update in-place all the tracked
ResourceImpls (including the one from the system context) using the new
application info. Thus, the system context has its resources updated,
despite its package info being stale.

From the system context is derived a system UI context, which has the
same underlying info. When creating a new context from this system UI
context, we try to initialize the resources based on the package info.
As this info is stale, we only have the base system resources, but we
are missing (along other state) the color overlays.

This ensures that the package info of the system context is also updated
when handling application info changes, so that any contexts created
from this one would have the correct state.

Flag: android.content.res.system_context_handle_app_info_changed
Test: atest testHandleApplicationInfoChanged_systemContext
Bug: 362420029
Change-Id: I027ce41419944e2af3c66cb753e7a0f97c8f57f3