[core] Revisit core commands, such as Find, Replace, Select All, Undo, and Redo

[kittaakos]

Description

Core commands do not have an active handler when no editors are open.

root ERROR Failed to execute command: Error: The command 'core.find' cannot be executed. There are no active handlers available for the command. (args: [null])
    at e.<anonymous> (https://a1b11df7-2f7c-4238-ba5e-663642a4eb98.ws-eu01.gitpod.io/bundle.js:1:88902)
    at https://a1b11df7-2f7c-4238-ba5e-663642a4eb98.ws-eu01.gitpod.io/bundle.js:1:85102
    at Object.next (https://a1b11df7-2f7c-4238-ba5e-663642a4eb98.ws-eu01.gitpod.io/bundle.js:1:85207)
    at https://a1b11df7-2f7c-4238-ba5e-663642a4eb98.ws-eu01.gitpod.io/bundle.js:1:84120
    at new Promise (<anonymous>)
    at a (https://a1b11df7-2f7c-4238-ba5e-663642a4eb98.ws-eu01.gitpod.io/bundle.js:1:83897)
    at e.executeCommand (https://a1b11df7-2f7c-4238-ba5e-663642a4eb98.ws-eu01.gitpod.io/bundle.js:1:88444)
    at e.executeKeyBinding (https://a1b11df7-2f7c-4238-ba5e-663642a4eb98.ws-eu01.gitpod.io/bundle.js:12:120459)
    at e.run (https://a1b11df7-2f7c-4238-ba5e-663642a4eb98.ws-eu01.gitpod.io/bundle.js:12:121395)
    at HTMLDocument.<anonymous> (https://a1b11df7-2f7c-4238-ba5e-663642a4eb98.ws-eu01.gitpod.io/bundle.js:12:290680)

The above error happens when you do Ctr/Cmd+F without an editor open. But you can try Undo, and Redo too by closing all editors and setting the focus to the SCM's textArea or SIW's input.

Related: #7339 (comment)

Reproduction Steps

OS and Theia version:

Diagnostics: