refactor: program runfiles

BREAKING CHANGE

This changes move program (to be run on the target device) runfiles logic from bazel/labgrid/runner to labgrid/run thus include_runfiles is removed from FileTransfer.

We cannot rely on assumption that program runfiles will be always next to the binary with <program.name>.runfiles location. This mostly happens when the labgrid_test rule and its src target are defined within separate bazel packages, e.g.:

# BUILD.bazel
py_binary(
    name: "to_run",
    ...
)

# test/subpackage/BUILD.bazel
labgrid_test(
    name = "test_me",
    src = "//:to_run",
    ...
)

To allow to search for program runfiles in different directory //labgrid/run:run introduces --program-runfiles-dir attribute.

Closes #77 (closed).