refactor(parameters): moved ssm resource creation to AwsCustomResource

[dreamorosi]

Description of your changes

As described in the linked issue (#1316), as part of the integration tests for the SSMProvider part of the Parameters utility we are creating some SecureString SSM resources. The creation of this type of resources was initially implemented with a Lambda-backed custom resource because CDK doesn't offer any L2 construct for them.

This PR refactor that portion of code to instead use AwsCustomResource. This allows to remove a significant amount of code and to not have to maintain a dedicated Lambda function whose single purpose was to create & delete these resources. With the usage of AwsCustomResource the responsibility of this function is moved to CDK instead.

Once merged, this PR will close #1316.

How to verify this change

See successful e2e test run here.

Related issues, RFCs

Issue number: #1316

PR status

Is this ready for review?: YES
Is it a breaking change?: NO

Checklist

• My changes meet the tenets criteria
• I have performed a self-review of my own code
• I have commented my code where necessary, particularly in areas that should be flagged with a TODO, or hard-to-understand areas
• I have made corresponding changes to the documentation
• I have made corresponding changes to the examples
• My changes generate no new warnings
• The code coverage hasn't decreased
• I have added tests that prove my change is effective and works
• New and existing unit tests pass locally and in Github Actions
• Any dependent changes have been merged and published
• The PR title follows the conventional commit semantics

Breaking change checklist

• I have documented the migration process
• I have added, implemented necessary warnings (if it can live side by side)

---

By submitting this pull request, I confirm that you can use, modify, copy, and redistribute this contribution, under the terms of your choice.