Add metrics-token secret to deployment

[saschagrunert]

What type of PR is this?

/kind feature

What this PR does / why we need it:

This allows referencing the metrics token from a stable secret name.

Which issue(s) this PR fixes:

Refers to #276

Does this PR have test?

None

Special notes for your reviewer:

None

Does this PR introduce a user-facing change?

Added `metrics-token` secret to the operator namespace for metrics client retrieval.

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: saschagrunert

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Needs approval from an approver in each of these files:

• OWNERS [saschagrunert]

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[codecov-commenter]

Codecov Report

Merging #457 (93406aa) into master (6ad33b2) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #457   +/-   ##
=======================================
  Coverage   37.17%   37.17%           
=======================================
  Files          23       23           
  Lines        1049     1049           
=======================================
  Hits          390      390           
  Misses        644      644           
  Partials       15       15           

[cmurphy]

/lgtm