Read default_minimal_size_resizable_task directly from Resources.

Remove scaling with DisplayMetrics obtain from system context, which can
be outdated. Also added check to guarantee that
default_minimal_size_resizable_task is in dp unit.

Bug: 270393438
Test: passes local atest

Change-Id: I1ad4cb7d2d44cce8de9a3d9acb074671549f777a