For historical reasons audio and video workloads were launching the
browser as part of their setup. This is no longer necessary. Not only
that, since on recent devices the default Android browser is missing,
this causes problems with the workloads. This commit removes the browser
launch.
Added -p option to the list command. This alows filtering results by
supported platforms, e.g.
wa list workloads -p linux
Also adding missing supported_platforms attribute to various extensions.
If an extension does not have this attribute, the assumption is that it
is supported by all available platforms.
