Consolidate pull-down menus

Work in progress.

* sly.el (sly-inspector-mode-map): Remove some invalid
keybindings.
(menubar-sly, menubar-sly-sldb): Removed.
(sly-menu, sly-sldb-menu, sly-inspector-menu): New menus.
(sly-sldb-easy-menu, sly-easy-menu): These variables are unneeded.
(sly-add-easy-menu, sly-sldb-add-easy-menu): Removed.

* contrib/sly-mrepl.el (sly-mrepl--last-prompt-overlay):
Resurrected.
(sly-mrepl-mode): Remove `sly-mrepl-mode-map' comint parent.
(sly-mrepl--shortcut-menu, sly-mrepl--menu): New menus.

* contrib/sly-trace-dialog.el (sly-trace-dialog--shortcut-menu)
(sly-trace-dialog--menu): New menus.
(sly-trace-dialog--menubar): Remove.
Fix SLDB problems after last refactoring

* sly.el (sldb-setup, sldb-insert-frames, sldb-insert-frame)
(sldb-frame-details-region): New function.
(sldb-frame-details-visible-p): Deleted.
(sldb-sugar-move,sldb-hide-frame-details, sldb-toggle-details):
Use `sldb-frame-details-region'
(sldb-sugar-move): Fix bug.
More sly-mrepl fixes

* sly-mrepl.el (sly-mrepl-mode-map): Add "M-p" and "M-n"
lost when `comint-mode-map' inheritance was broken.
(sly-mrepl--insert-output): Ensure prettier insertion of
unexpected async output.
* sly.el (sly-popup-buffer-mode-map): Must be `quit-window'