feat(e2e): Use binary that needs runfiles

This adds test coverage to binaries that need runfiles to run.

There seems to be a bug[1] which affects `py_binary`'s and causes its
output to include multiple files (which in turn forces us to use
$(locations <...>)). So I had to make my custom implementation of `cat`
extra hardcoded.

[1]: https://github.com/bazelbuild/bazel/issues/20038