Memtrack HAL: Remove MemtrackType::NUM_TYPES

Remove NUM_TYPES from MemtrackType enum, since this can cause conflicts
if the enum changes.

Use enum_range to iterate the MemtrackType enum.

Bug: 179432507
Test: atest VtsHalMemtrackTargetTest
Change-Id: Iadad3e0547c1c2f6aaf0f55a2d50e4c625a909e0
7 files changed