feat(amplify-appsync-simulator): add TransactWriteItems support

[chucre]

add TransactWriteItems support to DynamoDB operations

Add TransactWriteItems support to amplify-appsync-simulator

Issue #, if available:
implement aws-amplify/amplify-category-api#259

Description of changes:
Implement the missing TransactWriteItems operator to DynamoDB data loader

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[codecov]

Codecov Report

Merging #5574 into master will not change coverage.
The diff coverage is 0.00%.

@@           Coverage Diff            @@
##           master    aws-amplify/amplify-cli#5574    +/-   ##
========================================
  Coverage   59.08%   59.08%            
========================================
  Files         402      402            
  Lines       18043    18043            
  Branches     3575     3388   -187     
========================================
  Hits        10661    10661            
- Misses       6723     6743    +20     
+ Partials      659      639    -20     

Impacted Files	Coverage Δ
...ackages/amplify-cli/src/utils/mobilehub-support.ts	39.28% <0.00%> (ø)
...gen-appsync-model-plugin/src/utils/process-auth.ts	100.00% <ø> (ø)
packages/amplify-util-mock/src/api/api.ts	0.00% <0.00%> (ø)
packages/graphql-mapping-template/src/print.ts	34.65% <0.00%> (ø)
packages/amplify-util-mock/src/storage/storage.ts	0.00% <0.00%> (ø)
...ges/amplify-util-mock/src/CFNParser/stack/index.ts	0.00% <0.00%> (ø)
...es/amplify-util-mock/src/api/resolver-overrides.ts	0.00% <0.00%> (ø)
...es/graphql-transformer-core/src/stripDirectives.ts	35.29% <0.00%> (ø)
.../amplify-cli-core/src/state-manager/pathManager.ts	70.42% <0.00%> (ø)
.../amplify-util-mock/src/utils/lambda/loadMinimal.ts	0.00% <0.00%> (ø)
... and 11 more

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[lgtm-com]

This pull request introduces 1 alert when merging 520ebda into 43eb3e8 - view on LGTM.com

new alerts:

• 1 for Unused variable, import, function or class

[cheneveld]

@yuth @jhockett Any idea when this could be merged in?

[cheneveld]

@yuth Any chance we can move this PR forward?

[majirosstefan]

Dear Amplify team, would it be possible to merge this pull request after 1 year of ignoring it, please?

[staffanpalopaa]

Do I understand it correctly that this pull request has been waiting for over a year without any feedback?? For anyone who builds a complex multi user application it's absolutely essential to be able to run fast tests involving transactions!!

[a-marcel]

Any news here ? @yuth

[Amplifiyer]

Apologies for the delay. Started looking into this PR, only thing missing is testing. Please add some unit tests and if applicable, steps on how the change was tested locally.

[danielleadams]

@chucre are you still interested in making this contribution?