Update Structured Data Capture Library codelab

[jingtang10]

IMPORTANT: All PRs must be linked to an issue (except for extremely trivial and straightforward changes).

Description

• Remove some commented out code for user to copy+paste from codelab directly
• Use coroutine for extraction
• Fix issue where there isn't a questionnaire json string variable in the activity
• Add menu

Alternative(s) considered
Have you considered any alternatives? And if so, why have you chosen the approach in this PR?

Type
Choose one: Documentation

Screenshots (if applicable)

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).

[jingtang10]

thanks omar - comments addressed.

[omarismail94]

Nice change! 🎉

[codecov]

Codecov Report

Merging #1448 (d563167) into master (e17ee6e) will not change coverage.
The diff coverage is n/a.

@@            Coverage Diff            @@
##             master    #1448   +/-   ##
=========================================
  Coverage     85.68%   85.68%           
  Complexity      716      716           
=========================================
  Files           149      149           
  Lines         10768    10768           
  Branches        860      860           
=========================================
  Hits           9227     9227           
  Misses         1100     1100           
  Partials        441      441           

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