chore: upgrade metrics-server to v0.3.7

[jackfrancis]

Reason for Change:

This PR updates the delivered version of metrics-server to v0.3.7 for all supported Kubernetes versions. See:

https://github.com/kubernetes-sigs/metrics-server/releases

Issue Fixed:

Requirements:

• uses conventional commit messages
• includes documentation
• adds unit tests
• tested upgrade from previous version

Notes:

[mboersma]

Upgrade golang version to 1.12

Whoa slow down there metrics-server... 😆 (Go 1.15 is about to release.)

[mboersma]

/lgtm

[codecov]

Codecov Report

Merging #3669 into master will increase coverage by 0.05%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #3669      +/-   ##
==========================================
+ Coverage   73.10%   73.15%   +0.05%     
==========================================
  Files         147      147              
  Lines       25257    25301      +44     
==========================================
+ Hits        18463    18508      +45     
+ Misses       5657     5655       -2     
- Partials     1137     1138       +1     

Impacted Files	Coverage Δ
pkg/api/k8s_versions.go	100.00% <ø> (ø)
pkg/api/vlabs/types.go	71.83% <0.00%> (ø)
pkg/engine/template_generator.go	82.05% <0.00%> (+0.02%)	⬆️
pkg/api/types.go	94.31% <0.00%> (+0.06%)	⬆️
pkg/api/converterfromapi.go	94.17% <0.00%> (+0.07%)	⬆️
pkg/api/convertertoapi.go	93.68% <0.00%> (+0.07%)	⬆️
pkg/engine/templates_generated.go	53.42% <0.00%> (+0.15%)	⬆️
pkg/api/vlabs/validate.go	80.00% <0.00%> (+0.33%)	⬆️
pkg/engine/params.go	67.85% <0.00%> (+0.38%)	⬆️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 495dc66...df48a0a. Read the comment docs.

[jackfrancis]

/azp run pr-e2e

[azure-pipelines]

Azure Pipelines successfully started running 1 pipeline(s).

[mboersma]

/lgtm

[jackfrancis]

Initial test signal suggests that 1.15 doesn't work with (this) metrics-server v0.3 spec. So maybe we need to undo that change. Stay tuned.

[jackfrancis]

/hold

[jackfrancis]

/hold release

[mboersma]

/lgtm

[acs-bot]

[APPROVALNOTIFIER] This PR is APPROVED

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

The full list of commands accepted by this bot can be found here.

The pull request process is described here

Needs approval from an approver in each of these files:

• OWNERS [jackfrancis,mboersma]

Approvers can indicate their approval by writing /approve in a comment
Approvers can cancel approval by writing /approve cancel in a comment