fix(inputs): ignoring input events in IE caused by placeholder changes o...

...r focus/blur on inputs with placeholders

This is my attempt at fixing #8242 as well as the extra placeholder issues with focus/blur. I'm assuming I'm missing a weird test case that still breaks somewhere, but I still think this is an improvement (it definitely is for my use cases).
I think 'should dirty' is correct, but the rest of the name needs to change: 'should dirty the model on an input event while in focus even if a placeholder changed' or something like that...