Implement version detection for must-gather image selection

[coderabbitai]

Description

Currently, the must-gather command uses a hardcoded default image when the --image flag is not specified:

o.effectiveImage = "registry.redhat.io/oadp/oadp-mustgather-rhel9:v1.5"

As noted in the TODO comment in cmd/must-gather/must_gather.go, a future enhancement should automatically detect the installed OADP version and map it to the appropriate must-gather image.

Proposed Enhancement

• Detect the OADP operator version installed in the cluster
• Maintain a mapping of OADP versions to their corresponding must-gather images
• Automatically select the correct must-gather image based on the detected version
• Fall back to a reasonable default if version detection fails

References

• PR: Add must-gather command for diagnostic collection #115
• Comment: Add must-gather command for diagnostic collection #115 (comment)
• Requested by: @kaovilai