Hide unsupported targets

Currently if you select 4.1.0 the list of targets still includes the devices that were dropped in 4.x e.g. R9 or Ghost, if you select one of those and try to build it just results in a generic build error that says nothing useful and certainly doesn't point to the fact these targets were dropped.

Unsupported targets should be hidden based on the selected version.

Start by tracing how the selected version determines the displayed target list and where target availability is represented. Reproduce the issue by selecting 4.1.0, verify that dropped targets such as R9 and Ghost are excluded, and confirm supported targets remain available.

Written by the indexing model from the issue text.