Face tweaks in sly-mrepl and a shortcut to the debugger

* contrib/sly-mrepl.el (define-channel-method :prompt): Insert a button to
the associated debugger.
(sly-mrepl--prompt-face): Removed.
(sly-mrepl-prompt-face): Renamed from
`sly-mrepl-normal-prompt-face'
(sly-mrepl-errored-prompt-face): Removed.
Try to improve REPL prompt synchronization

* sly-mrepl.el (sly-mrepl--insert-prompt): Helper function for :prompt method.
(define-channel-method :write-values): Don't `accept-process-output' here.
(sly-mrepl-return): Do it here.
* swank-sbcl.lisp (frame-arguments): Implement for SBCL
Xref mode also uses buttons

* sly.el (sly-mode-map): `sly-next-location' and
`sly-previous-location' unbound.
(sly-xref-face, sly-xref, sly-xref-button): New button type, face
and constructor.
(sly-insert-xrefs): Insert buttons.
(sly-xref-prev-line, sly-xref-next-line): Use buttons.
(sly-next-location-function, sly-previous-location-function)
(sly-goto-next-xref, sly-goto-previous-xref, sly-next-location)
(sly-previous-location): Remove.
(sly-xref--show-buffer): Don't set `sly-next-location-function' or
`sly-previous-location-function'
Compilation notes also use buttons

* sly.el (sly-compilation-finished-hook): Remove option `sly-list-compiler-notes'.
(sly-load-failed-fasl): Change default to a saner option 'NEVER.
(sly-highlight-notes): Use `sly--add-in-buffer-note'.
(sly-note-overlays, sly-remove-old-overlays, sly-filter-buffers): Removed.
(sly-merge-notes-for-display, sly-merge-notes)
(sly-notes-in-same-location-p): Removed.
(sly-create-compilation-log): Enter `sly-mode' as well.
(sly-compilation-log--notes): New variable.
(sly-insert-compilation-log): Use buttons and fields.
(sly-overlay-note, sly-goto-note-in-compilation-log): Removed.
(sly-create-note-overlay, sly-merge-note-into-overlay): Removed.
(sly-choose-overlay-for-sexp, sly-choose-overlay-region)
(sly-choose-overlay-for-read-error): Replace `cl-values' with plain `list'
(sly-severity-face-plist): Fix indentation.
(sly-visit-source-path): Removed.
(sly-next-note): Simplify.
(sly-previous-note): Simplify.
(sly-goto-first-note): Simplify.
(sly-remove-notes): New function.
(sly-merge-notes): New function.
(sly-show-note): Redone.
(sly-temporarily-highlight-note): Removed.
(sly-note-at-point, sly-note-overlay-p)
(sly-note-overlays-at-point, sly-find-next-note)
(sly-find-previous-note): Removed.
(sly-note, sly-in-buffer-note, sly-compilation-note-group): New
button types.
(sly--in-buffer-note-modification, sly--add-in-buffer-note)
(sly--compilation-note-group-button): New functions.
(sly-filter-buffers): Moved to SLDB section where it's used.
(sly-menu): Replace `sly-list-compiler-notes' with
`sly-show-compilation-log'
Another 150 lines of useless window managing code gone

* sly.el (sly-read-package-name): Don't use `sly-bogus-completion-alist'
(sly-completions-buffer-name)
(sly-complete-saved-window-configuration, sly-completions-window)
(sly-complete-delay-restoration)
(sly-complete-forget-window-configuration)
(sly-complete-restore-window-configuration)
(sly-complete-maybe-restore-window-configuration)
(sly-completion-window-active-p, sly-display-completion-list)
(sly-display-or-scroll-completions, sly-scroll-completions): Removed.
(sly-simple-complete-symbol): Much simplified
(sly-complete-symbol): Use `completion-at-point-functions'
(sly-maybe-complete-as-filename): Removed, seems useless.
(sly-minibuffer-respecting-message): Removed.
(sly-indent-and-complete-symbol): Call `indent-for-tab-command'
(sly-bogus-completion-alist): Removed.
(sly-simple-completions): Removed.
Restore severity-related faces for in-buffer compilation notes

* sly.el (sly-most-severe): Removed.
(sly-merge-notes): Removed. Done in `sly--add-in-buffer-note'.
("pretty colors"): Remove reference to two macros which are gone.
(sly--add-in-buffer-note): Consider note severity.
* swank.lisp (dispatch-event): Fix typo.