[data] Improve download/upload error output

[kkozoriz]

Description

Problem

When d8 data export download or d8 data import upload commands encounter a not-ready resource, the error message is generic and unhelpful - e.g., DataExport ns/name is not Ready. Users have no way to understand the root cause (timeout, misconfiguration, controller issue, etc.) and cannot take corrective action.

Additionally, during the retry loop (up to 60 attempts), there is no intermediate feedback - the command appears to hang silently until it either succeeds or fails after ~3 minutes.

Solution

• Include Kubernetes condition Message and Reason fields in all "not Ready" error messages for both DataExport and DataImport resources. The error now reads: DataExport ns/name is not Ready: <message> (<reason>).
• Add periodic progress logging every 5th retry attempt (~15 seconds) in GetDataExportWithRestart and GetDataImportWithRestart, so users can see the current status and attempt number while waiting.

Before fix

After fix