feat: Add placeholder prop to <SelectArrayInput>

[erwanMarmelab]

Problem

<SelectArrayInput> cannot render a custom text when no choice is selected (e.g. "All Channels" in a filter).

Closes #10454.

Solution

Add a placeholder prop, rendered in place of the chips while the value is empty.

How To Test

http://localhost:9010/?path=/story/ra-ui-materialui-input-selectarrayinput--placeholder

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• The PR targets master for a bugfix or a documentation fix, or next for a feature
• The PR includes unit tests (if not possible, describe why)
• The PR includes one or several stories (if not possible, describe why)
• The documentation is up to date

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[erwanMarmelab]

This PR should target next. Here is the good PR -> #11327