Expose "InputElement" on qualified classes

[pranavkm]

Fixes #24446

Updated copy of #24899

[ghost]

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[pranavkm]

@javiercn could I get a sign off on this?

[javiercn]

But what about the perf!

[pranavkm]

It'll get fixed eventually. But no, all those delegates make me cringe a bit. If we wanted to, we could turn them in to static lambdas (by letting the callback include the sending component). We have one benchmark that tracks this scenario, we can see if this makes a big difference in the rendering perf.