[pickers] Add calendarHeader slot

[flaviendelangle]

Closes #6653
Closes #9783
Live example

[mui-bot]

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Updated pages

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These are the results for the performance tests:

Test case	Unit	Min	Max	Median	Mean	σ
Filter 100k rows	ms	318	455.6	352.1	373.18	55.83
Sort 100k rows	ms	481.7	874	725.9	703.1	144.202
Select 100k rows	ms	154.3	212.7	205.6	188.4	25.755
Deselect 100k rows	ms	126	267.3	179.8	183.4	51.038

Generated by 🚫 dangerJS against 589f369

[flaviendelangle]

The component had shouldDisableXXX props but never received them and never used them.
The new typing is closer from what is actually used.

[alexfauquette]

It overall looks good. I'm wondering if we should provide helpers to recreate the default header, by providing a <HeaderLabel/> and a <HeaderMonthSwich/> Such that if devs want to add something in the middle they can do it without having to care about stuff like: the labelId should be passed to the date text, I need to add some transition on buttons, ...

[github-actions]

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

[github-actions]

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

[github-actions]

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

[matheus1lva]

Would be good to also give the users a dropdown for the months and for the years, so we can have users that create a layout with one dropdown for each type.

[github-actions]

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

[LukasTy]

Should be a great improvement! 👏
Do you think it would be worth adding a section in the https://mui.com/x/react-date-pickers/custom-components/ page? 🤔

[dChin84]

♥️ That this feature is in the pipeline. Could I ask how long it would be until the release 👍

[flaviendelangle]

@dChin84 we can't guarantee a release date yet, hopefully next week

[LukasTy]

IMHO, it wouldn't hurt having example(s) on custom-componets page, but thats purely optional.
Great work! 👍 💯

[flaviendelangle]

I'll do a follow up with a doc example 👍

[gabrielbuii]

Hi! Is there a way to add a custom header for the digital clock section as well? A few users have mentioned they're having trouble distinguishing between the hour and minute columns... Essentially, we want to add a label above the hours, minutes, and seconds columns.