feat(mockServer): set preserveResolvers default to true

[cchen9299]

Description

Motivation and Context

americanexpress#253

How Has This Been Tested?

Tested locally with an OneApp module, but I'm unsure whether sharing screenshots of our local development screens in a public github PR breaches any American Express HR violation. I'm on Web and Mobile Slack!

Types of Changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation (adding or updating documentation)
• Dependency update

Checklist:

• My change requires a change to the documentation and I have updated the documentation accordingly.
• My changes are in sync with the code style of this project.
• There aren't any other open Pull Requests for the same issue/update.
• These changes should be applied to a maintenance branch.
• This change requires cross browser checks.
• This change impacts caching for client browsers.
• I have added the Apache 2.0 license header to any new files created.

What is the Impact to Developers Using parrot?