feat: add support for Kubernetes 1.19.1

[mboersma]

Reason for Change:

See https://github.com/kubernetes/kubernetes/blob/master/CHANGELOG/CHANGELOG-1.19.md/#changelog-since-v1190

Issue Fixed:

Requirements:

• Kubernetes artifacts built and pushed by Azure Pipelines
• uses conventional commit messages
• includes documentation
• adds unit tests
• tested upgrade from previous version

Notes:

1.19.1 artifacts are not yet published by Azure, so this will fail for now.

[jackfrancis]

/lgtm

[codecov]

Codecov Report

Merging #3816 into master will decrease coverage by 0.01%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #3816      +/-   ##
==========================================
- Coverage   73.20%   73.19%   -0.02%     
==========================================
  Files         148      148              
  Lines       25385    25394       +9     
==========================================
+ Hits        18583    18587       +4     
- Misses       5666     5671       +5     
  Partials     1136     1136              

Impacted Files	Coverage Δ
pkg/api/common/versions.go	96.84% <ø> (ø)
cmd/upgrade.go	42.71% <0.00%> (-1.50%)	⬇️
pkg/engine/templates_generated.go	53.42% <0.00%> (ø)
pkg/engine/engine.go	86.09% <0.00%> (+0.35%)	⬆️

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[acs-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: jackfrancis, mboersma

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