Validate during NN conversions by default -- hal

This change renames all `convert` functions to `unvalidatedConvert`.
This change also introduces new `convert` functions that act only on the
types that appear in the NN HIDL methods directly. These new `convert`
functions perform validation. Specifically, if either the source or
destination value is invalid, then the conversion fails.

Bug: 160667419
Test: mma
Test: NeuralNetworksTest_static
Change-Id: I492956ff60ad1466c67893993d28cdd6f3860708
Merged-In: I492956ff60ad1466c67893993d28cdd6f3860708
(cherry picked from commit 32acc061)