[tech debt] migrate catalogd command handling to cobra

[grokspawn]

Maintenance/update of https://github.com/operator-framework/catalogd/blob/main/cmd/manager/main.go flag handling would be greatly simplified by adopting https://github.com/spf13/cobra

[Horiodino]

Hi, I’m interested in working on this. If no one else is currently assigned, would it be alright if I take it on?

[LalatenduMohanty]

#1598 fixed this.