fix(cli): fix for code scanning alerts: Prototype-polluting assignment

[mrgrain]

Fix for https://github.com/aws/aws-cdk-cli/security/code-scanning/5 https://github.com/aws/aws-cdk-cli/security/code-scanning/6 https://github.com/aws/aws-cdk-cli/security/code-scanning/7

To fix the prototype pollution vulnerability, we need to ensure that the keys used in the deepSet function do not include any properties that can modify Object.prototype. This can be achieved by validating the keys in the path array and rejecting any keys that are __proto__, constructor, or prototype.

The best way to fix this problem without changing existing functionality is to add a validation step before using the keys in the path array. We will add a check to ensure that none of the keys in the path array are __proto__, constructor, or prototype.

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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

Attention: Patch coverage is 66.66667% with 8 lines in your changes missing coverage. Please review.

Project coverage is 84.96%. Comparing base (3791941) to head (f34c60d).

Files with missing lines	Patch %	Lines
...s/@aws-cdk/tmp-toolkit-helpers/src/util/objects.ts	66.66%	8 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #233      +/-   ##
==========================================
+ Coverage   84.88%   84.96%   +0.07%     
==========================================
  Files         208      208              
  Lines       35680    35701      +21     
  Branches     4616     4618       +2     
==========================================
+ Hits        30287    30333      +46     
+ Misses       5247     5218      -29     
- Partials      146      150       +4     

Flag	Coverage Δ
suite.unit	84.96% <66.66%> (+0.07%)	⬆️

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