[pickers] MultiSectionDigitalClock layout review

[arthurbalduini]

Extracted from #14397

When working on the PR mentioned above, it was noticed that currently the actionBar causes a stretch on the MultiSectionDigitalClock, causing UI issues:

Currently, we have a slight misalignment of the margins when two or more actions are available

I proposed some changes on the UI on that PR, but it led to discussions so it made sense to discuss it separately, where we can all discuss design changes. The image below illustrates the impacts of the change.

Some inputs to the discussions:

• Maybe in the future new actions can be added and impact the sizing even more
• Should the sections expand to use the stretched space caused by the actionBar?
• Should the buttons expand vertically and fill the whole section area ?
• This discussion might generate a solution that will also close [pickers] Time section scroll bar gets in front of section column #9311

[flaviendelangle]

As discussed in the main PR, the ownerState should comme from usePickerLayout.

But overall I have an issue with this BC because PickersLayoutContentWrapper is public so people will need to pass manually the ownerState and it's not a great DX IMHO.
We really need to rework the whole DX at some point to hide those implementation details.

[mui-bot]

Deploy preview: https://deploy-preview-15258--material-ui-x.netlify.app/

Generated by 🚫 dangerJS against 1a5c9d7

[noraleonte]

I think the design changes make sense in this case 👌
Just one small comment: I think it would make sense if the buttons within each section would stretch so that the text is centered 😸

[github-actions]

This pull request has conflicts, please resolve those before we can evaluate the pull request.

[flaviendelangle]

Once #15494 is merged, you should be able to just add pickerValueType to PickerOwnerState (I think it's worth adding it there since it's not specific to the layout).