Add attribute to DWO-injected commands that should not be displayed to users

[AObuchow]

Description

#1307 & #1329 added commands to devworkspaces with the name format init-ssh-agent-command-x. These commands are meant to be run automatically as postStart commands, rather than being invoked by users manually.

Currently, in Che we are [filtering out](che-incubator/che-code#445 these specific commands in the editor so that they are not displayed in the commands list.

However, a better approach would be to add an attribute to all DWO-injected commands that should not be displayed to the user. For example, controller.devfile.io/internal-command: true.

Additional context

Thank you for the suggestion @RomanNikitenko :)