Test TOCTOU in VTS CompilationCachingTests.

Two tests are added into VTS:

1. The TOCTOU test, for a fixed number of iterations.

We try to attack the driver by replacing the model cache with another
cache entry from a similar model while the driver is saving to or
preparing from cache, and see if the driver crashes or falsely prepares
an unexpected model (by checking the execution result). Either of the
following results are acceptable

* Fails -> the driver detects this corruption.
* Succeeds and produces correct execution result -> the corruption
happens before saving to cache or after preparing from cache.

Due to the racy nature, this test is probabilistic and we run it several
times.

2. Similar to the TOCTOU test but replace the content between
compile-to-cache and compile-from-cache (once only).

Additionally, remove tmp cache directory if test succeeds.

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: Check /data/local/tmp and confirm that
      * dirs are preserved on failure
      * dirs are removed on success

Change-Id: Ie04fa905f465c3775979f0ca74359d185dcacea9