Disable reduced scale if reduced scale config is 0

Change reduced scale implementation to toggle on/off based on
config_lowResTaskSnapshotScale=0 instead of ro.config.low_ram=true

Also, only use _reduced.jpg if reduced scale is enabled.  Previously,
for task snapshots, [0-9]+_reduced.jpg would be used if reduced scale
was disabled, and [0-9]+.jpg would never be used. This patch swaps that
behavior to make the underlying system more intuitive.  Now, if reduced
snapshots are disabled, store the task snapshot in [0-9]+.jpg and never
use [0-9]+_reduced.jpg.

Also, store low-res snapshots at config_lowResTaskSnapshotScale.
Prevously, low-res snapshots were stored at lowResScale * highResScale

Test: TaskSnapshotCacheTest
Test: TaskSnapshotControllerTest
Test: TaskSnapshotPersisterLoaderTest
Test: TaskSnapshotSurfaceTest
Bug: 148099851
Bug: 142063079
Change-Id: I5a0d58766347d875eaec138820323063aa1c2988