* [1742] Ensure multiple composite annoations are correctly written.
This implementation uses a collector pattern to allow embedded ExecutionContexts to stash Issue objects for later processing by a non-embedded ancestor ExecutionContext.
Also:
- Provide explicit constructor implementations for ExecutionContext
- Leverage explicit constructors to solidify immutability of several ExecutionContext class members.
- Fixed erroneous call to ExecutionContext.Complete in CompositeActionHandler.cs
- Use a consistent timestamp for FinishTime in ExecutionContext::Complete
* Ensure collected issues are processed only by a non-embedded ExecutionContext.
This was already implicit. Now, just making it explicit.
* Provide a clear mechanism that allows callers to opt-in/opt-out of ExecutionContext::AddIssue's logging behavior.
* Addressed deserialization inconsistencies in TimelineRecord.cs
* Added TimelineRecord unit tests.
* Refined unit tests related to TimelineRecord::Variables case-insensitivity
* Add a unit test that verifies ExecutionContextLogOptions::LogMessageOverride has the desired effect.
* Responded to PR feedback.
* Don't allow embedded ExecutionContexts to add Issues to a TimelineRecord
