Added onChange/requestChange support to LinkedInput

[Dachaz]

For LinkedInput to be actually useful as a replacement for valueLink/checkedLink on regular input elements, it needs to trigger requestChange of the ReactLink object. This can be achieved by this one-line change.

I wanted to add a corresponding test, but for tests to work for me locally, I had to revert parts of #7168, which I assume is going in a wrong direction.

A couple of additional notes on the tests:

• Currently, they're not captured by grunt test as both the folder name is wrong and the packages folder is not in testPathDirs of package.json
• When fixing the previous issue, and getting jest to find this package's tests, they fail on require statements. I had an idea on how to fix this, but it looked to me as if it would break npm packaging of react-linked-input and since I couldn't find instructions on how to build that package, I gave up on fixing the tests.

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[aweary]

Thanks for the PR @Dachaz! At this point, I don't think we're going to be making changes to LinkedInput. We don't recommend using the two-way binding helpers and per #8854 it's likely that packages like this will be fully deprecated in favor of community maintained alternatives.