fix(material-experimental/mdc-chips): decouple removal from animation

[mmalerba]

Currently the MDC chips automatically trigger an animation that collapses the chip to 0x0 dimensions, but it still keeps it in the DOM unless the consumer updates their data source. This is misleading and there's no way for the consumer to see it.

These changes bring the chip in line with our current behavior where we only dispatch the remove event and then it's up to the consumer to remove the chip.

Making these changes also revealed some tests that were passing by accident and weren't actually testing the things they were supposed to, because the animationend event wasn't being dispatched. I've tweaked them in order to get them to work as expected.

Fixes #21561.

CARETAKER NOTE: This was previously merged and broke internal tests. Pantheon's harnesses will need to be updated to work with this change

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