[pickers] Add deprecations when importing pickers from the lab

[flaviendelangle]

• I have followed (at least) the PR section of the contributing guide.

The pickers have been moved to @mui/x-date-pickers since the 12th of April 2022.
Until now, we were re-exporting everything in @mui/lab without warning to give some time to stabilize them before forcing a migration.
But we now need to end the transition phase which is causing package duplication to some users using both @mui/x-date-pickers and @mui/lab for other components.
This PR adds clear warnings when using a picker component from the lab that those are deprecated.
The pickers will stop being re-exported from the lab during the 1st release of July 2022, at that point we will keep the warning but will not render anything anymore (like for DateRangePicker in @mui/lab currently).

[mui-bot]

Details of bundle changes

@material-ui/lab: parsed: +2.57% , gzip: +0.98%

Generated by 🚫 dangerJS against 61eaffd

[oliviertassinari]

I thought we already had these deprecations 😁

Could we expand on the PR's description of why we need to make the removal happen so soon (4 weeks/releases down the line)? It might have been discussed on Slack, but nobody from the community has access to this discussion. Thanks

[DanailH]

I've also opened a follow-up PR to remove the pickers doc page under the Lab section -> #32961

[oliviertassinari]

But we now need to end the transition phase which is causing package duplication to some users using both @mui/x-date-pickers and @mui/lab for other components.

@flaviendelangle Thanks for the context, so I assume it's meant to help fix mui/mui-x#4569.

As far as I know, only Option 0 or Option C will solve mui/mui-x#4569 at the root. Here, removing the dependency on July 1st is what I assume is a step in Option A. Sure it will help with this problem but not solve the root, I'm not sure that it's we need to go this far. It seems that the deprecation will be what will have the most impact. If a developer faces the error of mui/mui-x#4569, after this PR, he will get a deprecation warning giving a tip on what to do next.

So personally, I would advocate for the lab to keep the dependency on the pickers, until Material UI v6, to make it so developers can update Material UI v5 at their own pace to get React 18 support.
Alternatively, we could move slower, add the deprecations, and reevaluate in 4 weeks to see if we need the next step. However, another value of removing the dependency of the pickers in the lab could be to get more accurate npm download stats.

[mnajdova]

Nice, this should allow developers to have better transition 👍