Add new partial to handle feature flags

[lamATnginx]

Proposed changes

• Added new partial to handle "feature flag"-like hugo params for Coveo + Qualtrics for example.
• Refactored old flag check for Coveo and Qualtrics.

Checklist

Before creating a PR, run through this checklist and mark each as complete.

• I have read the CONTRIBUTING document
• If applicable, I have added tests that prove my fix is effective or that my feature works
• If applicable, I have checked that any relevant tests pass after adding my changes
• I have updated any relevant documentation (README.md and CHANGELOG.md)

[github-actions]

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[nginx-jack]

Could you do a build of the documentation repo with --templateMetrics enabled, and see if there's any major build time impacts?
Thinking about it, we should add a little performance check to our builds, in case we add a new shortcode that ends up really slowing the build time.

[nginx-jack]

Also worth adding a "how to" for feature flags to the example site itself.

Feel free to do that in another PR, I've approved, so resolve and merge these comments if you need.

[lamATnginx]

Could you do a build of the documentation repo with --templateMetrics enabled, and see if there's any major build time impacts? Thinking about it, we should add a little performance check to our builds, in case we add a new shortcode that ends up really slowing the build time.

We have lighthouse in our pipeline.