Move getSupportedOperations out of saveToCache.

Before this change, getSupportedOperations_1_2 was invoked in
saveModelToCache prior to prepareModel_1_2, which delayed the model
preparation and cache overwriting always ran faster in
SaveToCache_TOCTOU test.

This change increases the chance that the model is overwritten after it
is saved in SaveToCache_TOCTOU test by moving getSupportedOperations_1_2
out of saveToCache.

Bug: 123433989
Test: VtsHalNeuralnetworksV1_xTargetTest with 1.2 sample driver
Test: VtsHalNeuralnetworksV1_xTargetTest with a test driver that can
      read and write cache entries
Test: TOCTOU tests with a sample driver that is deliberately broken

Change-Id: Ieba6a82252623ac429d5fcb6950b99db949f9886