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
• Code follows the standards mentioned here
• Updated relevant documentation
• Re-reviewed Files changed in the Github PR explorer
• Added appropriate labels

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

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

Additional details and impacted files

@@                    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	Coverage Δ
unittests	42.17% <100.00%> (+0.14%)	⬆️

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