Add plugin for testing method tracing speed.

It can be useful to test how much overhead the ART method tracing
infrastructure has. Since normal method tracing APIs (eg
-Xmethod-trace, JVMTI events) have significant overhead for
synchronization or other reasons we created a simple plugin that
begins method tracing but doesn't record or even look at the trace
events. This lets us have a rough idea how much simply sending these
events costs us.

Test: ./test/run-test --host \
         --runtime-option \
         -Xplugin:$ANDROID_HOST_OUT/lib/libtracefast-trampolined.so \
         001-Main

Change-Id: I1fac4cdd0dfa780cb4efe195025b3d29e8cf619c