Handle transaction result errors in `flow migrate stage`

[jribbink]

Description

Errors while staging a contract (related to a failed transaction) are not properly reported. This handles that case.

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For contributor use:

• [ ] Targeted PR against master branch
• [ ] Linked to Github issue with discussion and accepted design OR link to spec that describes this work
• [x] Code follows the standards mentioned here
• [ ] Updated relevant documentation
• [x] Re-reviewed Files changed in the Github PR explorer
• [x] Added appropriate labels

[codecov-commenter]

Codecov Report

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

Project coverage is 42.17%. Comparing base (ad513f5) to head (401fb13).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## feature/stable-cadence #1607 +/- ## ========================================================== + Coverage 42.02% 42.17% +0.14% ========================================================== Files 60 60 Lines 4200 4202 +2 ========================================================== + Hits 1765 1772 +7 + Misses 2200 2197 -3 + Partials 235 233 -2 ``` | [Flag](https://app.codecov.io/gh/onflow/flow-cli/pull/1607/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=onflow) | Coverage Δ | | |---|---|---| | [unittests](https://app.codecov.io/gh/onflow/flow-cli/pull/1607/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=onflow) | `42.17% <100.00%> (+0.14%)` | :arrow_up: | Flags with carried forward coverage won't be shown. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=onflow#carryforward-flags-in-the-pull-request-comment) to find out more.

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