Add forward proxy support to Plus mgmt config

[AlexFenlon]

Proposed changes

• add controller.mgmt.usageReport.proxyHost and controller.mgmt.usageReport.proxyCredentialsSecretName to helm
• add usage-report-proxy-host to the mgmt ConfigMap
• add docs
• add unit, helm tests and template tests
• expand hostname regex to support up to 63 characters for TLD

Checklist

Before creating a PR, run through this checklist and mark each as complete.

• I have read the CONTRIBUTING doc
• I have added tests that prove my fix is effective or that my feature works
• I have checked that all unit tests pass after adding my changes
• I have updated necessary documentation
• I have rebased my branch onto main
• [] I will ensure my PR is targeting the main branch and pulling from my branch from my own fork

[github-actions]

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 52.15%. Comparing base (bca1685) to head (9443b17).
Report is 5 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #7560      +/-   ##
==========================================
+ Coverage   52.06%   52.15%   +0.09%     
==========================================
  Files          89       89              
  Lines       21312    21340      +28     
==========================================
+ Hits        11096    11130      +34     
+ Misses       9746     9741       -5     
+ Partials      470      469       -1     

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