Adjust code in response to Burst validation tests

This CL includes three changes in response to the Burst validation
tests:
(1) it cleans up the validation code in both ExecutionBurstServer and
    ExecutionBurstController to handle missed edge cases
(2) it alters IBurstExecutorWithCache's caches to use a map instead of
    an indexed vector to handle cases where non-NN runtime clients use
    sparse slots
(3) it combines the ValidationTest calls of "validateModel" and
    "validateRequest" into a generic "validateEverything"

Bug: 129779280
Bug: 129157135
Test: mma
Test: VtsHalNeuralnetworksV1_2TargetTest (with sample-all)
Change-Id: Ie06235ee19ea7d8173f7ac02f620c83e15705370