[multimod] Improve error message when Go proxy misbehaves

[mx-psi]

• Check status code of reply from Go proxy and fail if status code is 4xx or 5xx.
• Add information about package and tag that caused the failure

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 53.10%. Comparing base (06a3912) to head (be1f84f).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #610 +/- ## ========================================== + Coverage 53.03% 53.10% +0.06% ========================================== Files 51 51 Lines 2255 2258 +3 ========================================== + Hits 1196 1199 +3 Misses 912 912 Partials 147 147 ```

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