Add back @p to out parameters

[bernardnormier]

Issue #5276 (fixed by #5280) was not correct, and we should revert the commit.

@p to an out parameter is semantically correct in Slice and when this Slice out parameter is mapped to a language out parameter.

The actual issue is the mapping, and the context or lack of context while mapping the comment (summary, parameter comment, return comment) in C# and other languages. We should rework the comment-mapping to provide sufficient context when mapping @p references. If the referenced parameter is not there, we can map it like a @c.

[InsertCreativityHere]

Yes that is the other option I mentioned in my PR. I’ll revert and update the language mappings to handle it.

It’s worth noting this actually doesn’t affect most languages anyways, since most lack any special “paramref” syntax. So they get mapped to code-formatting anyways.

[InsertCreativityHere]

I reverted my PR (see fb69a9a), and opened a new PR with the option 2 (advocated by this issue): #5300

[InsertCreativityHere]

@p are always allowed now (since they're semantically correct even for out parameters).
But the language mapping was changed so that out-parameters always map to code-formatting.
This was done by #5300.

We can improve this for the 2 languages that have @p (C++) and <paramref ... /> (C#), but not sure if it's worth it.
out parameters are not mapped as out parameters for async or marshaled-result operations. Additionally @p and @c are equivalent in C++ anyways. Can always revisit improving the mapping in the future if we want.