feat(k8s): kosmos: add-external-node command

[Mia-Cross]

Closes #2955

Left to-do:

• Doc review
• Verify remote history

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 31.86813% with 62 lines in your changes missing coverage. Please review.

Project coverage is 55.27%. Comparing base (5bf53e0) to head (ccca392).
Report is 595 commits behind head on master.

Files with missing lines	Patch %	Lines
internal/namespaces/k8s/v1/custom_pool.go	31.11%	61 Missing and 1 partial ⚠️

❗ There is a different number of reports uploaded between BASE (5bf53e0) and HEAD (ccca392). Click for more details.

HEAD has 1 upload less than BASE

Flag	BASE (5bf53e0)	HEAD (ccca392)
	2	1

Additional details and impacted files

@@             Coverage Diff             @@
##           master    #4651       +/-   ##
===========================================
- Coverage   75.45%   55.27%   -20.18%     
===========================================
  Files         202      309      +107     
  Lines       44323    78993    +34670     
===========================================
+ Hits        33444    43666    +10222     
- Misses       9653    33926    +24273     
- Partials     1226     1401      +175     

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