generator should pull parameter names from Javadoc

[jonpryor]

Related? PR #687.

Parameter names remains an ongoing concern. "Best" is if the Java code is built with javac -parameters, which allows class-parse to extract parameter names, and everything is good.

Unfortunately, that still appears to be a rarity in the Java world.

Lacking javac -parameters, how should bindings get decent parameter names? A "reasonable" answer is to integrate @(JavaSourceJar) support, which with PR #687 and dotnet/android#5253 will parse @(JavaSourceJar) with java-source-utils.jar (69e1b80) to extract Javadoc and parameter names.

However, PR #687 is focused on parsing the Javadoc comments and translating them into C# XML Documentation Comments.

We should also look into using generator --with-javadoc-xml=FILE to determine parameter names as well.

Then there's the "priority" question: I think it would be most "sensible" and documentable if the last "source of truth" for parameter names was used in the bindings:

1. class-parse output.
2. java-source-utils.jar output
3. Metadata.xml updates

This would allow Metadata.xml to always override.

[jonpryor]

On further consideration, I don't think this requires any changes to generator.

Instead, we should update the _ExportJarToXml target so that the output of java-source-utils.jar is provided to ClassParse.DocumentationPaths. This will cause java-source-utils.jar output to be treated identically to Javadoc HTML input files regarding parameter names.