Add license token string to cluster spec

[sp1999]

Issue #, if available:
#2855

Description of changes:
This PR adds a new optional licenseToken string to the cluster spec for extended kubernetes version support.

Testing (if applicable):

make eks-a
make build-all-test-binaries
make lint
make unit-test
make generate
make generate-manifests
make release-manifests

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[sp1999]

/approve

[eks-distro-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: sp1999

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 72.42%. Comparing base (1b040bf) to head (d70d156).
Report is 4 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #9112   +/-   ##
=======================================
  Coverage   72.41%   72.42%           
=======================================
  Files         578      578           
  Lines       45589    45592    +3     
=======================================
+ Hits        33015    33018    +3     
  Misses      10838    10838           
  Partials     1736     1736           

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[sp1999]

/hold

[sp1999]

/unhold