edify: Move the testcases to gtest.

Now they live in tests/component/edify_test.cpp.

Also rename edify/main.cpp to edify/edify_parser.cpp. It becomes a
host-side debugging tool that validates the input edify script. However,
it supports edify builtin functions only and doesn't recognize the ones
defined via updater.

Test: recovery_component_test passes on device.

Change-Id: Ib94a787bf15098a9cc078d256b6a6dc96ff12b2e