TASK: deprecate and disable not use-full and broken keyboard shortcuts

[mhsdesign]

Related #4153
Related #3100

We have discussed thousand times that our keyboard shortcuts are too absurd to be useful and that we want to free the space in the ui and reduce complexity in the code for a feature which doesnt really work.

Notice the missing button? Me neither

Neos.Neos.Ui.frontendConfiguration.enableLegacyKeyboardShortcuts allows to re-enable it in case its really used somewhere and might then lead us to not removing it in 9.3

[Sebobo]

I think there a valid reasons to keep some of the shortcut functionality as I also have plugins that register useful shortcuts and it would be awesome if Neos still provides the API to handle them properly from host or guest frame. For example my AddNodeButton, the Commandbar, Terminal, stuff like that.
But I think almost everyone dislikes the random shortcuts solely based on letters.

[mhsdesign]

Hmm external plugins huhm maybe we should provide an extension point for these things indeed but it will look fully different (and work next time) i dont think we should continue to provide the current extension point for plugins. The whole things needs new and plugins could at first attach their own event listeners.

[Sebobo]

IMO we can only move the button somewhere in 9.2 so it doesn't bother so much anymore, but not throw everything away.
For 9.3/10 I would like to have a RFC with the team.

[mhsdesign]

i think a feature flag for 9.2 is also ok ... thats why i proposed this ... we talked about fully removing it already but yes thats definitely too much for 9.2 now