Android: Change directory before running tests
Android: Run benchmarks and copy metrics
auto merge of #8642 : sanxiyn/rust/arm-test, r=catamorphism

`stdtest` and `extratest` expects to be able to write to `tmp` directory under the current working directory, so the first commit creates `tmp` directory and changes the directory before running tests.

The second commit adds `--bench` argument to test runs and copies metrics from the remote device.