[scheduler][joy] Allow to group events by "resource"

[flaviendelangle]

Follow up on #17695 (the logic should also apply to any other view created so far)

In this PR:

• Add a new property on the event model (something like resourceId?: number) to define to which resource the event belongs (would be the ID of the Agenda in Google Calendar for instance)
• Add a new resources?: SchedulerResource[] prop to define stuff like the event color or the name of the resource
• Allow to set a color per resource and render the event with the right background.
• Allow to edit the resource on an event if [scheduler][joy] Add event editing inside a popover / drawer #17704 is merged (this field should be customizable in the future because depending on the kind of data the resource represent, you don't want to label it "Resource").

Not in this PR:

• Create the UI to only render some resources (those resources could be grouped in bigger categories like on Google Calendar) - [scheduler][joy] Allow to only render events from certain resources #17842
• Create a UI to render each resource in a standalone grid / timeline.
• Allow to have several resources associated to a single event

Google Calendar (Event Calendar):

Bryntum (Event Calendar):

MobiScroll (Timeline):

MobiScroll (Event Calendar):