v2.0.2: Check if label should float based on validity (#271)

* Check if label should float based on validity

Number inputs can have allowed characters that aren't numbers (-,e) and won't
trigger a value change and thus not float the label.

However, the validity will report badInput so we can trigger a label float by
setting it to something truthy but still not visible.

Fixed in paper-input 3.x

See #229
RM Solves #19930

* rename handler, use input event, add test

* update test to trigger handler

Doesn't actually test the behavior, can't find a way to properly
emulate a keypress.

* onBadInputFloatLabel - add test for bad Events

Signed-off-by: Patrik Kullman <patrik.kullman@neovici.se>