SF: Clean up FakeDisplayDeviceInjector TODO

Split the double-duty setDisplayModes API.

Bug: 241285876
Test: libsurfaceflinger_unittest
Change-Id: Id52a824d22c9a89b650a9c50d0093b95ecfd9123
Merged-In: Id52a824d22c9a89b650a9c50d0093b95ecfd9123
(cherry picked from commit aa73cf5ade78f45dac0ba6feb03f0501b7b80ead)
3 files changed