Add new airgapped plugin as standalone plugin

[Vandy-P]

Signed-off-by: Vandana Pathak pathakv@sjc-ubu-eng-127.vmware.com

What this PR does / why we need it

Add custom image repository pre-loading command to Tanzu CLI to replace bash script hack for users in airgapped environments
CLI Plugin - isolated-cluster

Commands -

• download-bundle - Download images/bundle into local disk as TAR.
• upload-bundle - Upload images to private repository

Ex :

tanzu isolated-cluster download-bundle --source-repo --tkg-version --source-ca-certificate/--source-insecure

tanzu isolated-cluster upload-bundle --source-directory --destination-repo --destination-ca-certificate/--destination-insecure  

Which issue(s) this PR fixes

Fixes # 4093

Describe testing done for PR

• Run tanzu isolated-cluster download-bundle with version v1.6.0 , its downloading all the tar files and yaml as expected.(with insure mode)
• Run tanzu isolated-cluster upload-bundle with destination repo Azure ACR , its uploading all the images to acr.

Release note

CLI Plugin  - isolated-cluster

Commands - 
- download-bundle   - Download images/bundle into local disk as TAR.  
- upload-bundle - Upload images to private repository

Complete Command :
 
tanzu isolated-cluster download-bundle --source-repo --tkg-version --source-ca-certificate/--source-insecure

tanzu isolated-cluster upload-bundle --source-directory --destination-repo --destination-ca-certificate/--destination-insecure  

Additional information

Special notes for your reviewer

Please refer to this PR #3743 for review discussion and approval. (We had to revert the PR for some build issue .)

[codecov]

Codecov Report

Merging #4103 (3d0816c) into main (a334b86) will decrease coverage by 0.78%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##             main    #4103      +/-   ##
==========================================
- Coverage   48.52%   47.74%   -0.79%     
==========================================
  Files         446      469      +23     
  Lines       44105    45569    +1464     
==========================================
+ Hits        21404    21756     +352     
- Misses      20658    21753    +1095     
- Partials     2043     2060      +17     

Impacted Files	Coverage Δ
cmd/cli/plugin/cluster/credentials_update.go	8.73% <0.00%> (ø)
cmd/cli/plugin/cluster/set_machinehealthcheck.go	23.33% <0.00%> (ø)
cmd/cli/plugin/cluster/scale.go	17.85% <0.00%> (ø)
cmd/cli/plugin/cluster/get.go	6.27% <0.00%> (ø)
cmd/cli/plugin/cluster/get_node_pools.go	10.52% <0.00%> (ø)
cmd/cli/plugin/cluster/available_upgrade.go	16.32% <0.00%> (ø)
...i/plugin/cluster/delete_machinehealthcheck_node.go	16.66% <0.00%> (ø)
cmd/cli/plugin/cluster/upgrade.go	58.94% <0.00%> (ø)
...cluster/delete_machinehealthcheck_control_plane.go	16.66% <0.00%> (ø)
...in/cluster/get_machinehealthcheck_control_plane.go	11.11% <0.00%> (ø)
... and 14 more

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[Vandy-P]

Please don't delete this branch.