LinkFieldDefinitionConverter doesn't treat properly `targetTreeRootPath` property

From what it looks like the converted chooser gets its datasource definition resolved only via the specified app's content connector definition, but the old link field actually also allows specifying `workspace` and `rootPath` properties explicitly and those aren't considered by the converter.

AC:

• mentioned two properties are handled (:?: and passed to the CompatibilityAppAwareWorkbenchChooserDefinition#resolveDatasourceFromAppName)
• test case is written (can piggyback on the linked Blossom issue)