libs/utils/android/system: Add systrace configuration
libs/utils/android/system: Add systrace configuration

For workloads with collect='systrace', systrace can now be
configured in a similar manner to ftrace. Simply add a systrace
dict in the TestEnv conf like so:

"systrace" : {
    "events" : [
        "gfx",
        "view",
        "sched",
        "freq",
        "idle"
    ],
    "buffsize" : 100 * 1024
}

credp/lisa,ARM-software/lisa,credp/lisa,ARM-software/lisa,credp/lisa,ARM-software/lisa,ARM-software/lisa,credp/lisa