Camera2 framework stress test suite

Added a new Camera2 framework stress test to put stress in
the common use cases in exercising Camera2 APIs.

Note that this stress test differs from Camera CTS in that
it focus on ensuring stability rather than functionality.
It could also provide the flexibility to get integrated with
test tools if needed.

For the initial run, most test codes are taken from CTS package
except for test fixtures to handle arguments and results for
stress test. However test implementation could be differentiated
to meet needs in stress testing over time.

Change-Id: Ie36594de3904e41f6175b8d5072b91941975d091