Do not need the 'Add action button' if the corresponding strategy exists

Created by: LinuxSuRen

As I mentioned in the subject, we don't need it. For example, I already added 'Discover Branches' as a branches scanning strategy, the button 'Discover Branches' still exists. The most important thing is that nothing happened when I try to click it.

See the screenshot below:

Suggestion

• Make the corresponding button be invisible if the strategy exists
• Disable the button 'Add Action' if all strategies are added

/area devops