kapp-controller leader election should provide safety during update operations

**Describe the problem/challenge you have**
- no way to configure leader election for kapp-controller

**Describe the solution you'd like**
- we'd like a better guarantee for limiting the number of *active* kapp-controller reconcilers to 1 during rolling upgrades of our cluster

**Anything else you would like to add:**
[Additional information that will assist in solving the issue.]

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