DynamoDB: transact_write_items() should return failing item

[bblommers]

Closes #5204

[codecov-commenter]

Codecov Report

Merging #5482 (970aee3) into master (5739db4) will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master    #5482   +/-   ##
=======================================
  Coverage   96.10%   96.10%           
=======================================
  Files         724      724           
  Lines       72059    72059           
=======================================
+ Hits        69250    69252    +2     
+ Misses       2809     2807    -2     

Flag	Coverage Δ
servertests	37.10% <0.00%> (ø)
unittests	96.04% <100.00%> (+<0.01%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
moto/dynamodb/exceptions.py	100.00% <ø> (ø)
moto/dynamodb/models/__init__.py	93.61% <100.00%> (ø)
moto/iam/models.py	95.62% <0.00%> (+0.12%)	⬆️

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[github-actions]

This is now part of moto >= 4.0.4.dev11