Handle indexing of timing with no event or has a repeating timing.

[aditya-07]

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

Fixes #1282

Description

1. Skip timings if they don't have an event to specify start and end date.
2. Handle string values for date time.

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

Type Choose one: Bug fix

Screenshots (if applicable)

Checklist

• [x] I have read and acknowledged the Code of conduct.
• [x] I have read the Contributing page.
• [x] I have signed the Google Individual CLA, or I am covered by my company's Corporate CLA.
• [x] I have discussed my proposed solution with code owners in the linked issue(s) and we have agreed upon the general approach.
• [x] I have run ./gradlew spotlessApply and ./gradlew spotlessCheck to check my code follows the style guide of this project.
• [x] I have run ./gradlew check and ./gradlew connectedCheck to test my changes locally.
• [x] 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).

[codecov[bot]]

Codecov Report

Merging #1419 (a0ddee4) into master (4bda160) will increase coverage by 85.72%. The diff coverage is 81.25%.

:exclamation: Current head a0ddee4 differs from pull request most recent head 744edca. Consider uploading reports for the commit 744edca to get more accurate results

@@              Coverage Diff              @@
##             master    #1419       +/-   ##
=============================================
+ Coverage          0   85.72%   +85.72%     
- Complexity        0      719      +719     
=============================================
  Files             0      149      +149     
  Lines             0    10773    +10773     
  Branches          0      859      +859     
=============================================
+ Hits              0     9235     +9235     
- Misses            0     1098     +1098     
- Partials          0      440      +440     

Impacted Files	Coverage Δ
...a/com/google/android/fhir/index/ResourceIndexer.kt	85.57% <81.25%> (ø)
...src/main/java/com/google/android/fhir/MoreDates.kt	100.00% <0.00%> (ø)
...ogle/android/fhir/datacapture/MoreAnswerOptions.kt	69.23% <0.00%> (ø)
...s/QuestionnaireItemPhoneNumberViewHolderFactory.kt	90.00% <0.00%> (ø)
...oogle/android/fhir/sync/download/DownloaderImpl.kt	100.00% <0.00%> (ø)
...acapture/contrib/views/barcode/mlkit/md/TaskExt.kt	0.00% <0.00%> (ø)
...d/fhir/search/filter/NumberParamFilterCriterion.kt	100.00% <0.00%> (ø)
...m/google/android/fhir/index/entities/TokenIndex.kt	100.00% <0.00%> (ø)
...a/com/google/android/fhir/index/ResourceIndices.kt	88.73% <0.00%> (ø)
...droid/fhir/datacapture/utilities/MoreLocalTimes.kt	100.00% <0.00%> (ø)
... and 140 more

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