[mdc-slider] change event always firing on mousup or keypress

[devversion]

Bug report

Steps to reproduce

1. Go to https://material-components.github.io/material-components-web-catalog/#/component/slider

2. Open dev-tools

3. Select the slider demo element

4. Enter the following into the console: $0.addEventListener('MDCSlider:change',d => console.error('Change event'));

5. Click on the slider thumb multiple times (preferably on the most left; so that the value can't change). Notice that the change event still emits without value change.

6. Press left arrow until you are at value = 0. Notice that if you continue pressing left arrow keys the change event is still emitted.

Actual behavior

Change event always fires. Even if value didn't change.

Expected behavior

Change event only fires if there is a "change". Ideally the "change" event would follow native-input event semantics and only fire

Software	Version(s)
MDC Web	^4.0.0-alpha.0
Browser	Chrome
Operating System	Windows

Related to angular/components#16795