Move prepareModel cache file logic to Manager file

Bug: N/A
Test: mma
Test: NeuralNetworksTest_static
Test: CtsNNAPITestCases
Change-Id: I940a6fd78324b0ccb845b01985887c583efc8fc1
Merged-In: I940a6fd78324b0ccb845b01985887c583efc8fc1
(cherry picked from commit fa30144c450b538b8f599a38b12b56ce2601b800)
4 files changed