fix(collapse): restore previous transition logic

[divdavem]

This PR restores the previous collapse transition logic that was changed with #4370.

Without this PR, the show and hide phases are inconsistent: the hide phase is from the full size of the container to 0px, and the show phase is from 0px to the scrollWidth/scrollHeight of the container and then there is a sudden change when the classes are changed at the end of the transition.

Using scrollWidth / scrollHeight does not feel right for me. We should use whatever size the container will have when changing the classes at the end of the transition, which is what measureCollapsingElementDimensionPx measures correctly. I have added style="max-width:300px;" on the container in the demo so that the animation matches the visible content.

Before submitting a pull request, please make sure you have at least performed the following:

• read and followed the CONTRIBUTING.md and DEVELOPER.md guide.
• built and tested the changes locally.
• added/updated any applicable tests.
• added/updated any applicable API documentation.
• added/updated any applicable demos.

[maxokorokov]

LGTM, thanks. It is better like this indeed

[divdavem]

@maxokorokov Thank you for reviewing and merging my PR!