Expose raw events for OnColumnGroupOpened and OnGridReady

[Larocceau]

For the OnGridReady and OnColumnGroupOpened, instead of mapping the AgGrid API directly, we expose a limited set of utility functions:

static member onColumnGroupOpened(callback: _ -> unit) = // This can't be inline otherwise Fable produces invalid JS
    let onColumnGroupOpened =
        fun ev ->
            {|
                AutoSizeGroupColumns =
                    fun () ->
                        // Runs the column autoSize in a 0ms timeout so that the cellRenderer cells render before
                        // the grid calculates how large each cell is
                        JS.setTimeout
                            (fun () ->
                                let colIds =
                                    ev?columnGroups
                                    |> Seq.head
                                    |> fun cg -> cg?children
                                    |> Array.map (fun x -> x?colId)

                                ev?api?autoSizeColumns colIds)
                            0
                        |> ignore
            |}
            |> callback

static member onGridReady(callback: _ -> unit) = // This can't be inline otherwise Fable produces invalid JS
    let onGridReady =
        fun ev ->
            {|
                AutoSizeAllColumns =
                    fun () ->
                        // Runs the column autoSize in a 0ms timeout so that the cellRendererFramework cells render
                        // before the grid calculates how large each cell is
                        JS.setTimeout
                            (fun () ->
                                let colIds = ev?api?getColumns () |> Array.map (fun x -> x?colId)
                                ev?api?autoSizeColumns colIds)
                            0
                        |> ignore
                Export = fun () -> ev?api?exportDataAsCsv (obj ())
            |}
            |> callback

This severely restricts the flexibility the user has in handling this event; there should be an overload for these that just exposes the event:

type AgGrid<'row> =
   ....
   static member onGridReady(OnGridReadyEvent -> unit)
   static member onColumnGroupOpened (OnColumnGroupOpenedEvent -> unit)

The utility functions can be implemented using type extensions on the event (or most cases even the grid API), located in a separate module to make it clear that these are not native AGGrid features

I suggest deprecating the current event handlers, as the behaviour of having multiple of these events is undefined

[Larocceau]

A few other event handlers that are exposed weirdly:

on AgGrid:
onCellEditRequest: has signature (obj -> unit)
onCellValueChanged: specifically calls it's function on the event data
onRowClicked: specifically calls the callback on a limited number of event fields
onSelectionChanged: specifically calls the callback on the selected rows
onRangeSelectionChanged: specifically calls the callback on a limited number of event fields

on ColumnDef:
onCellClicked: specifically calls the callback on the selected rows