Implement Trackable as an extension property

[JPercival]

• This PR changes the ELM graph to no longer inherit from Trackable. That was done because Java doesn't have a way to to "mix-in" functionality to existing classes (partial classes, extension methods, etc.). Kotlin instead supports extension properties.
• Serialization code no longer needs to handle the Trackable elements as transient
• In Java code, this still needs to be accessed via Trackable.INSTANCE. This will go away once more code is converted
• This change precipitated changes in the ELM visitor. The method changes were converted to be non-null.

[github-actions]

Formatting check succeeded!

[codecov]

Codecov Report

Attention: Patch coverage is 70.27027% with 55 lines in your changes missing coverage. Please review.

Project coverage is 65.97%. Comparing base (82823a8) to head (1686713).
Report is 1 commits behind head on feature-kotlin.

Files with missing lines	Patch %	Lines
...ramework/cql/elm/evaluation/ElmAnalysisHelper.java	15.78%	12 Missing and 4 partials ⚠️
...java/org/cqframework/cql/cql2elm/LibraryManager.kt	11.11%	6 Missing and 2 partials ⚠️
...java/org/cqframework/cql/cql2elm/Cql2ElmVisitor.kt	62.50%	4 Missing and 2 partials ⚠️
.../org/cqframework/cql/cql2elm/tracking/Trackable.kt	75.00%	4 Missing ⚠️
...ds/cqf/cql/engine/execution/EvaluationVisitor.java	42.85%	2 Missing and 2 partials ⚠️
...mework/cql/cql2elm/tracking/WeakIdentityHashMap.kt	89.65%	1 Missing and 2 partials ⚠️
...cqframework/cql/elm/requirements/TypeResolver.java	0.00%	3 Missing ⚠️
...m/requirements/fhir/DataRequirementsProcessor.java	66.66%	1 Missing and 2 partials ⚠️
...java/org/cqframework/cql/cql2elm/LibraryBuilder.kt	81.81%	0 Missing and 2 partials ⚠️
...org/cqframework/cql/elm/visiting/BaseElmVisitor.kt	83.33%	2 Missing ⚠️
... and 4 more

Additional details and impacted files

@@                 Coverage Diff                  @@
##             feature-kotlin    #1472      +/-   ##
====================================================
+ Coverage             65.91%   65.97%   +0.05%     
- Complexity             4860     4881      +21     
====================================================
  Files                   489      490       +1     
  Lines                 28785    28797      +12     
  Branches               5433     5421      -12     
====================================================
+ Hits                  18974    18999      +25     
+ Misses                 7593     7587       -6     
+ Partials               2218     2211       -7     

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[sonarqubecloud]

Quality Gate failed

Failed conditions
69.4% Coverage on New Code (required ≥ 80%)

See analysis details on SonarQube Cloud