Revert^2 "Add an @Inject-able MobileSignalControllerFactory"

This is step (1/n) towards refactoring the networking iconography stack
in sysui. This change moves the creation of the MobileSignalController
to an injectable factory as a precursor to reducing the dependencies
between NetworkControllerImpl and its managed subcontrollers.

Test: atest SystemUITests
Bug: 238425913

b1971c77

Change-Id: I81119853a2cc97c7a69af78fab382fd0e4201dd8