cmd/retrieve: allow skip check and set namespace when retrieving from SB

[mtulio]

Introduce flags --skip-check and --namespace when retrieving results to allow the command retrieve get results from Standalone executions executed by sonobuoy subsystem. It will take advantage of retry engine implemented in OPCT to prevent issues like that when using native retrieve:

$ opct sonobuoy retrieve
error retrieving results: unexpected EOF

Then now:

$ opct retrieve -n sonobuoy -s
INFO[2024-08-22T17:16:50-03:00] Collecting results...                        
INFO[2024-08-22T17:17:02-03:00] Results saved to /home/mtulio/openshift-labs/opct-base-07/opct_202408221911_b6643aa2-c1dc-4c06-a70e-0185aa79f00a.tar.gz 
INFO[2024-08-22T17:17:02-03:00] Use the results command to check the validation test summary or share the results archive with your Red Hat partner. 

[openshift-ci]

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