Need to update [DebuggerDisplay] attributes to match renamed field names

[KirillOsenkov]

See here, for example:
https://github.com/Microsoft/msbuild/blob/master/src/XMakeBuildEngine/Instance/ProjectPropertyGroupTaskInstance.cs#L23

Field name is _condition, however DebuggerDisplay references condition.

As a result, these objects are difficult to inspect in the debugger.

[KirillOsenkov]

[AndyGerlicher]

We should definitely do this!