Add standalone weather view to lockscreen if decoupling isenabled.

At the same time, filters the WEATHER target for the existing
BcSmartspaceView.

The standalone weather view is also controlled via
LockscreenSmartspaceController, alongside the existing BcSmartspaceView.
Together they replace the keyguard_slice_view when the SMARTSPACE flag
is set. Note: keyguard_slice_view is the "legacy" smart space prior to
the introduction of BcSmartspace.

Reusing LockscreenSmartspaceController to control the new view has other
advantages as well.
  1. We can keep just one SmartspaceSession and one session listener.
  2. We can reuse all the existing logic. For example, the logic to
     update the text color when the theme changes, or via region
     sampling.

Also: cleaned up the unused @Named(LOCKSCREEN_SMARTSPACE_TARGET_FILTER)
from SmartspaceModule.kt.

Bug: 261752855
Bug: 265840309
Test: manual
Test: atest LockscreenSmartspaceControllerTest
Change-Id: Ib19b3178f3f7208693de973d0c7ff20ae4310e0a