fix(serverVariables): refresh state on definition change

[tim-lai]

Description

In the servers component, add a check to compare the default values of the the server variables between previous and next props. If there is a difference, this suggests a change in definitions, so apply a new default value that will overwrite a user selected value from the previous definition. Note that it is possible for both the server variable keys and values to be equal across different definitions.

Motivation and Context

fixes #7392

How Has This Been Tested?

New Cypress E2E tests

Screenshots (if appropriate):

https://recordit.co/RguJjDkPF5

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.