Fix multiple inspectors hopefully

* sly.el (sly-eval-for-inspector): Accept opener kwarg. Pass
current and target inspector to swank.
(sly-read-inspector-name): Fix typo.
(sly-inspector-part): Read inspector-name when clicking buttons.
(sly-inspector-fetch): Use `sly-eval-for-inspector'

* contrib/sly-trace-dialog.el (sly-trace-dialog): `pop-to-buffer'
smartness, but should be using `sly-with-popup-buffer'

* lib/lisp/swank.lisp (:compile-toplevel): New utility helper.
(*current-inspector*): Renamed from *INSPECTOR*
(*target-inspector*): New var.
(target-inspector): New function.
(current-inspector): Check boundness of variable.
(current-istate): Take optional inspector.
(eval-for-inspector): Must take current and target inspector.

* lib/lisp/swank.lisp (print-object): New printer for inspector
objects.