Windows: implement run_binary rule

[laszlocsomor]

Implement @laurentlb 's idea (from bazelbuild/bazel#7503 (comment)):

We can provide a simple rule in skylib:

exec_cmd(
  name = "x",
  tool = "//pkg:binary_to_run",
  args = ["-a", "-o", "$(location output_file)"],
  outputs = ["output_file", "logs"],
  stdout = "file_that_will_contain_stdout",
  stderr = "file_that_will_contain_stderr",
]

It executes a command, we can specify arguments, and we can save stdout and/or stderr to an output file. This should be able to replace many basic uses of genrule, right? And we can support this on all platforms.

[laszlocsomor]

Crucially this rule should use ctx.actions.run and NOT ctx.actions.run_shell, to avoid depending on Bash.