fix(try-it-out): required boolean default value set to empty string

[tim-lai]

Description

• Restored allowedValue to accept either enumValue or booleanValue.
  This will allow a boolean to have an empty default value, regardless of the if the field is required. On load (operation expanded), a required boolean field no longer inaccurately displays as true. Therefore a user must select a valid boolean value in order to execute the request.

• Created new Cypress tests to test rendering and validation of required enum and boolean fields.
  This also includes a test to validate that an optional empty value is NOT sent.

Motivation and Context

fixes #6429

How Has This Been Tested?

New Cypress tests.

Screenshots (if appropriate):

Checklist

My PR contains...

• No code changes (src/ is unmodified: changes to documentation, CI, metadata, etc.)
• Dependency changes (any modification to dependencies in package.json)
• Bug fixes (non-breaking change which fixes an issue)
• Improvements (misc. changes to existing features)
• Features (non-breaking change which adds functionality)

My changes...

• are breaking changes to a public API (config options, System API, major UI change, etc).
• are breaking changes to a private API (Redux, component props, utility functions, etc.).
• are breaking changes to a developer API (npm script behavior changes, new dev system dependencies, etc).
• are not breaking changes.

Documentation

• My changes do not require a change to the project documentation.
• My changes require a change to the project documentation.
• If yes to above: I have updated the documentation accordingly.

Automated tests

• My changes can not or do not need to be tested.
• My changes can and should be tested by unit and/or integration tests.
• If yes to above: I have added tests to cover my changes.
• If yes to above: I have taken care to cover edge cases in my tests.
• All new and existing tests passed.