feat(instance): add ssh utility commands

[Codelax]

Closes #3101

[codecov-commenter]

Codecov Report

Merging #3161 (5e89268) into master (eb63a03) will decrease coverage by 0.11%.
The diff coverage is 73.31%.

@@            Coverage Diff             @@
##           master    #3161      +/-   ##
==========================================
- Coverage   75.78%   75.68%   -0.11%     
==========================================
  Files         173      176       +3     
  Lines       37719    38222     +503     
==========================================
+ Hits        28585    28927     +342     
- Misses       8103     8230     +127     
- Partials     1031     1065      +34     

Impacted Files	Coverage Δ
...ternal/namespaces/instance/v1/custom_ssh_config.go	60.88% <60.88%> (ø)
internal/namespaces/instance/v1/custom_ssh_key.go	84.37% <84.37%> (ø)
internal/namespaces/instance/v1/custom.go	98.21% <100.00%> (+0.13%)	⬆️

... and 6 files with indirect coverage changes