Cleanup the constants in NeuralNetworks.h

- Alphabetize the operations.
- Move the constants that count operation and types
 out of the public header file.
- Remove N_GRAM operation.
- Add TENSOR_INT32.
- Add static assert verifications.
- Add documentation.

Test: Compiled and ran the tests.
Bug: 63905942

Change-Id: Ifafdcb3fd00efabd2b1972b035cc5d43f7dbec51
8 files changed
tree: 7feb23ced6f1d9f4c99777e8b6ee15e7ff3f29a5
  1. nn/
  2. Android.bp