Improve IDL hover

[milesziemer]

Already in-progress #166, this is for tracking purposes.

We're missing hover content on a few places:

• Members + elided members, should show only member name + target + traits and docs
• Node value members - same as above (like within trait values, metadata values, if applicable)

We can also improve the actual hover content, like moving the shape docs out of the code block, for example:

is kind of noisy - I would rather render the documentation in their own section.