Contributes to #9881

Context

When TaskParameterEventArgs represents an output parameter of a task, it currently does not capture the name of the parameter. This information is generally useful as multiple output parameters can be assigned to the same item, and it's important for the BuildCheck infrastructure to provide a consistent object model to build analyzers.

Additionally, output parameters that are assigned to properties are currently logged as textual log messages Output Property: {0}={1} which miss the name of the parameter as well.

Changes Made

Added two new properties on the TaskParameterEventArgs class, including the requisite serialization support. Updated logging to populate the properties with the name of the task parameter and the name of the build property, respectively, and updated BuildCheck infra to expose it to analyzers subscribed to task parameter events.

All task parameters are now logged as the structured TaskParameterEventArgs and the kind of parameter (input, output to property, output to item) can be determined by examining the args.

Testing

• Tweaked existing unit test and updated the relevant BuildCheck test.
• Verified that when using the standard console logger, the resulting textual log is identical.
• Verified that binlog viewer without the corresponding changes displays the forward-compat warning about unknown data.

Notes

• Complementary binlog viewer PR: Add support for improved TaskParameterEventArgs KirillOsenkov/MSBuildStructuredLog#780
• The change is behind a changewave because it is technically a breaking change for third party loggers.