With this option, only extensions packaged with WA itself will be
listed. Extensions discovered from other packages or from local paths
will not appear in the list.
- standardisded on a single context argument
- removed Device.init() no longer necessary as initilize now
automatically gets propagated up the hierarchy. Renamed the existing
use of it to "initilize".
- related pylint cleanup.
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.
