Provide more details of why a cherry-pick or revert failed in the UI
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### Problem to solve
https://gitlab.com/gitlab-org/gitlab/-/issues/33178 offers an error code in the API response clarifying what is the issue that prevented a cherry-pick from finishing successfully. However, that information isn't show in the UI. This might be confusing in the case of a cherry-pick conflict, as the default error message doesn't suggest that the error might be due to a conflict.
### Intended users
* [Delaney (Development Team Lead)](https://about.gitlab.com/handbook/marketing/product-marketing/roles-personas/#delaney-development-team-lead)
* [Sasha (Software Developer)](https://about.gitlab.com/handbook/marketing/product-marketing/roles-personas/#sasha-software-developer)
### User experience goal
The user should be able to figure out quickly why the cherry-pick didn't finish successfully.
### Proposal
Add more details as to why the cherry pick didn't go through
### Documentation
### Links / references
ZD https://gitlab.zendesk.com/agent/tickets/156986 (internal)
issue