In commit eaf365cb3e we explicitly sorted
them for neatness, with the rationale that we were restoring intentional
behavior and we only need a set for stylistic purposes.
This actually wasn't true, because we never sorted them to begin with
(we did sort the version numbers), but sorting them is fine. The bigger
issue is that we actually used a set to avoid printing the same feature
type multiple times. Now we do print them multiple times -- because each
registered feature includes the unique node.
Fix this by using both sorted and a set.
Fix tests that should in retrospect have flagged this as an issue, but
were added later on in the same series to check something else entirely,
happen to cover this too, and were presumably copied directly from
stdout as-is...
Currently Meson allow the following (Muon does not):
```meson
option('foo', type : 'boolean', value : 'true')
option('bar', type : 'integer', value : '42')
```
This is possibly a holdover from very old code, but it's a bad idea and
we should stop doing it. This deprecation is the first stop on that
journey.
Josh Soref