Cleanup HalInterfaces.h

Prior to this CL, HalInterfaces.h polluted the global namespace through
the "using" declarations. This CL creates a new ::android::nn::hal
namespace and places the names there instead.

This CL also changes the namespace of the Callback objects from
::android::hardware::neuralnetworks::V1_2::implementation to
::android::nn to be consistent with the other parts of frameworks/ml/nn.

Fixes: 72880287
Test: mma
Change-Id: I399ad32f5c541a493429c6fa8e192169a903ea9f
diff --git a/nn/common/ExecutionBurstServer.cpp b/nn/common/ExecutionBurstServer.cpp
index 28f73e2..74bc340 100644
--- a/nn/common/ExecutionBurstServer.cpp
+++ b/nn/common/ExecutionBurstServer.cpp
@@ -29,6 +29,8 @@
 namespace android::nn {
 namespace {
 
+using namespace hal;
+
 constexpr Timing kNoTiming = {std::numeric_limits<uint64_t>::max(),
                               std::numeric_limits<uint64_t>::max()};