[v0.13.x] - Allow an AntiAffinty tolerant to help ensure even spread of DNS pods

[dominicgunn]

Changes

• Adds a preferred scheduling anti-affinity to try and target nodes in different AZs if enabled.

Useful in situations where we have autoscaling enabled or are deploying DNS pods to nodes.

[k8s-ci-robot]

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[codecov-io]

Codecov Report

Merging #1672 into v0.13.x will decrease coverage by <.01%.
The diff coverage is 0%.

@@            Coverage Diff             @@
##           v0.13.x   #1672      +/-   ##
==========================================
- Coverage    25.41%   25.4%   -0.01%     
==========================================
  Files           98      98              
  Lines         5064    5065       +1     
==========================================
  Hits          1287    1287              
- Misses        3634    3635       +1     
  Partials       143     143

Impacted Files	Coverage Δ
pkg/api/types.go	0% <ø> (ø)	⬆️
pkg/api/cluster.go	0% <0%> (ø)	⬆️

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[davidmccormick]

/lgtm