Summary

Changes

Please provide a summary of what's being changed

This PR migrates the Parser utility tests to use Vitest, and while doing so, also streamlines the test structure to adhere the following guidelines:

• Each test should import/read only files that are relevant to that test
• When testing event payloads for AWS Services, focus on tests that verify the actual behavior of schemas and transforms (i.e. having two identical events for API Gateway where one differs only in the path field containing a trailing slash is useless since we don't validate/parse the path beyond ensuring it's a string).
• Follow conventions set in the codebase and avoid type casts and suppressions unless strictly necessary

Please add the issue number below, if no issue is present the PR might get blocked and not be reviewed

Issue number: closes #3247

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