Initial setup of a SystemMemoryTest.

Set up a memory test to experiment with actionable memory metrics and
detect regressions in system server memory use.

The initial CUJ is to launch an instrumentation that does nothing for
a few seconds.

The initial metric is to read showmap for system_server and report
VSS, RSS, and PSS.

The CUJ and metrics will be made more interesting once the basic
infrastructure for continuously running the test is set up.

Bug: 111830582
Test: tradefed.sh run commandAndExit template/local_min --template:map test=system-memory-test

Change-Id: I8793adb66de4adab254173585e2c8afc754d4a3a