fix: vtl list utils & update model test scenarios

[SwaySway]

Description of changes

Issue #, if available

Description of how you validated changes

Checklist

• PR description included
• yarn test passes
• Tests are changed or added
• Relevant documentation is changed or added (and PR referenced)
• New AWS SDK calls or CloudFormation actions have been added to relevant test and service IAM policies

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

[codecov-commenter]

Codecov Report

Merging #8701 (cd8fb5c) into master (14921fe) will increase coverage by 0.00%.
The diff coverage is 79.16%.

@@           Coverage Diff           @@
##           master    #8701   +/-   ##
=======================================
  Coverage   57.15%   57.15%           
=======================================
  Files         728      728           
  Lines       41195    41209   +14     
  Branches     8445     8453    +8     
=======================================
+ Hits        23546    23555    +9     
- Misses      16837    16842    +5     
  Partials      812      812           

Impacted Files	Coverage Δ
...ppsync-simulator/src/utils/auth-helpers/helpers.ts	80.95% <ø> (ø)
...ppsync-simulator/src/utils/graphql-runner/index.ts	100.00% <ø> (ø)
...es/amplify-appsync-simulator/src/velocity/index.ts	73.13% <28.57%> (-5.56%)	⬇️
...-appsync-simulator/src/velocity/util/list-utils.ts	100.00% <100.00%> (ø)
packages/amplify-util-mock/src/velocity/index.ts	100.00% <100.00%> (ø)

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[ammarkarachi]

[github-actions]

👋 Hi, this pull request was referenced in the v6.4.0 release!

Check out the release notes here https://github.com/aws-amplify/amplify-cli/releases/tag/v6.4.0.