[inspector] Misc improvements

[alexander-yakushev]

Nothing user-facing here except removing eval-and-inspect.

The controversial change of using vector for :rendered is in its own commit. No tests added because of Clojure's list/vector equality semantics. Besides, :rendered still becomes a seq in the end for now, until this transformation is moved into cider-nrepl instead.

[bbatsov]

Nice changes! Thanks!