Add HTTPS port variables

[nak3]

This patch adds HTTPS port variables.

Part of knative/serving#12501.

/cc @evankanderson @ZhiminXiang @carlisia

[codecov]

Codecov Report

Merging #640 (3258a05) into main (ec52d71) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main     #640   +/-   ##
=======================================
  Coverage   94.56%   94.56%           
=======================================
  Files          38       38           
  Lines         810      810           
=======================================
  Hits          766      766           
  Misses         31       31           
  Partials       13       13           

Impacted Files	Coverage Δ
pkg/apis/networking/ports.go	100.00% <ø> (ø)

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[nak3]

knative/serving#12770 is the code to demonstrate how to use this variables.

[ZhiminXiang]

/lgtm

[knative-prow-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: nak3, ZhiminXiang

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