platform_data does not forward Args or other Providers

[cramertj]

platform_data returns a DefaultInfo provider, discarding other providers from the original rule.

It also does not forward the args of the wrapped rule, so e.g. a py_binary with an args = [ ... ] parameter will not have its args provided when invoked through a platform_data rule.

[tpudlik]

@katre @aranguyen

[katre]

If there's a standard provider we can add it to the list to copy, but there's no way to programatically discover all providers of a dependency.

[fmeum]

This was solved for env by replacing the magic attribute with a provider. bazelbuild/bazel#16430 set out to do this but stalled - happy to revive it when there is consensus on the design.

[gregestren]

The args issue is specifically for --run_under=my_wrapped_py_binary?

I think a simple $ bazel run :my_wrapped_py_binary still works, doesn't it?