[scheduler][primitives] Allow to expand / shrink an event duration using drag & drop in the Time Grid

[flaviendelangle]

People should be able to edit the duration of an event by dragging the start of the end of the event vertically.

Screencast.2025-05-06.08.27.55.mp4

In this PR

• Add a prop on the TimeGrid.Event part to enable this behavior
• Add a areItemsResizable prop on the Event Calenar component and store it in state.areItemsResizable
• Pass state.areItemsResizable in the DayTimeGrid to every event rendered
• Allow to expand / shrink an event by dragging its start or end time
• Correctly round the duration (hardcoding the rounding to 15mn for now)

Not in this PR:

• Allow drag&drop across several days (if it's easy we can do it, but don't hesitate to split the work)
• Not in this PR: allow to enable / disable this behavior on specific events or resources
• Add constraints (only expand, only drag the start, only drag the end etc...)

[github-actions]

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