feat(expansion-panel): Export animation constants

[petosorus]

Feature Description

Hi! I'm implementing an expandable row in a mat-table as in this example https://material.angular.io/components/table/examples#table-expandable-rows

For now, I've copied the animation code as is, but I'm noticing it's the same as expansion panel. I'd like to import the expansion panel animations to ensure consistency in case material changes it.

I don't think it's exported and I can't import it.
If it's doeable but I missed it, I'd like the assist.
If not and it's something that'd be cool, I could do a PR on it, but I'm not too versed in module management.

Use Case

Implement a collapsable/expandable table and keep up with material updates via material constants