Changes in response to NNAPI QoS API Review

This CL makes the following changes:
* Remove #ifdef around enum constants (e.g. PriorityCode).
* Clarifies that *_setTimeout calls must be completed or aborted
  within the timeout duration
* Adds a way to restore timeout duration to the default value (i.e.,
  infinite)

As part of removing #ifdef around enum constants, DurationCode was
moved up in NeuralNetworks.h to be next to the other enums.

Bug: 148954238
Bug: 146082566
Test: mma
Test: CtsNNAPITestCases
Test: NeuralNetworksTest_static
Change-Id: I9fe1c7a25aa20603dea77603f5a7fccbabca1f6b
Merged-In: I9fe1c7a25aa20603dea77603f5a7fccbabca1f6b
(cherry picked from commit c16015f506777d2377d6ee1a4c814a3b1236397b)

runtime/ExecutionBuilder.cpp

diff --git a/runtime/ExecutionBuilder.cpp b/runtime/ExecutionBuilder.cpp
index caede71..f263991 100644
--- a/runtime/ExecutionBuilder.cpp
+++ b/runtime/ExecutionBuilder.cpp
@@ -325,7 +325,11 @@
         LOG(ERROR) << "ANeuralNetworksExecution_setTimeout called after the execution has started.";
         return ANEURALNETWORKS_BAD_STATE;
     }
-    mTimeoutDuration = duration;
+    if (duration > 0) {
+        mTimeoutDuration = duration;
+    } else {
+        mTimeoutDuration.reset();
+    }
     return ANEURALNETWORKS_NO_ERROR;
 }