Add utility functions for supporting CloudFormation CustomResources

[flostadler]

This change adds utility methods needed for supporting CloudFormation custom resources.

The main part of this change is a method for deeply converting all primitive values in a map[string]interface{} to strings. This is needed because CloudFormation has this behavior: https://github.com/aws-cloudformation/cloudformation-coverage-roadmap/issues/1037

[flostadler]

This change is part of the following stack:

• 1808 ◀

  • 1806

    • 1807

_{Change managed by git-spice.}

[github-actions[bot]]

Does the PR have any schema changes?

Looking good! No breaking changes found. No new resources/functions.

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 92.50000% with 3 lines in your changes missing coverage. Please review.

Project coverage is 46.78%. Comparing base (eafde1c) to head (4cd4ddb). Report is 1 commits behind head on master.

Files with missing lines	Patch %	Lines
provider/pkg/naming/convert.go	90.00%	2 Missing and 1 partial :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #1808 +/- ## ========================================== + Coverage 46.51% 46.78% +0.27% ========================================== Files 42 42 Lines 6127 6164 +37 ========================================== + Hits 2850 2884 +34 - Misses 3050 3052 +2 - Partials 227 228 +1 ```

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