Regenerate engine docs

[williamito]

Description
Regenerates documentation for FHIR Engine library. This PR is unfortunately noisy because the Engine docs were generated last time with a different version of Dokka, so a lot of the changes are just formatting. This should be less of a problem in the future, and if we do upgrade Dokka later we should try to regenerate the previous version of the SDK first so we can get a clean diff of changes.

Alternative(s) considered
Documentation generation step needs to be better integrated into release process in the future.

Type
Documentation

Checklist

• I have read and acknowledged the Code of conduct.
• I have read the Contributing page.
• I have signed the Google Individual CLA, or I am covered by my company's Corporate CLA.
• I have discussed my proposed solution with code owners in the linked issue(s) and we have agreed upon the general approach.
• I have run ./gradlew spotlessApply and ./gradlew spotlessCheck to check my code follows the style guide of this project.
• I have run ./gradlew check and ./gradlew connectedCheck to test my changes locally.
• I have built and run the demo app(s) to verify my change fixes the issue and/or does not break the demo app(s).