Cache ExecutionBurstServer memory resources

This change enables caching of memory resources. Prior to this CL, a
hidl_memory object in an execution burst had to be mapped and unmapped
on each execution, taking ~10us of time. With this change, a driver
could choose to map the hidl_memory when it is first retrieved, and
unmap when the burst is freed or when IContext::freeMemory is called.

Bug: 126244806
Test: mma
Test: atest NeuralNetworksTest_static
Test: atest VtsHalNeuralnetworksV1_0TargetTest (with sample-all)
Test: atest VtsHalNeuralnetworksV1_1TargetTest (with sample-all)
Test: atest VtsHalNeuralnetworksV1_2TargetTest (with sample-all)
Change-Id: I92d7632f2e1e2f5e76c63249d4c615c9af9d1acb
Merged-In: I92d7632f2e1e2f5e76c63249d4c615c9af9d1acb
(cherry picked from commit dfc94136aff39efdfb81436cee7e73c3f6834785)