Replacing App View toggle with separate toggles for showing code and stdout/stderr

[leventov]

Motivation: buttons should still be present in the App View: #5385

I think it would be more useful to actually retire the current "App View" toggle and instead replace it with two other toggles:

• Show/Hide all cell's code - completely, not like the effect of the cell-level "Hide code" option that keeps a single greyed-out line of code from the cell.
• Show/Hide standard outputs (logs): stdout and stderr. Probably as a single toggle, or perhaps as two separate ones.

Note: cell-level buttons for running/stopping the cells (especially useful in "on cell change: lazy" mode) and cell-level errors/exceptions are always visible. On the latter: currently, in the "App View", if there is an exception on the cell level, it's completely undiscoverable. It looks like nothing just happened: no pop-up, no indication that anything went wrong, nothing. It's like a website that doesn't work because of some javascript error, but you won't find out until you will open DevTools and look in the console. Since whatever exception happened will be discoverable in the javascript console even if "Edit View" is disabled (so, there are no security implications of this), I don't think hiding exceptions is useful for 99% of Marimo users.

In addition to solving usability problem #5385 and the usability problem described just above (exceptions are "silent" in the App View"), it would also bring sometimes useful options to hide all code at once without hiding logs, or vice versa, hiding logs without hiding code.

cc @akshayka