[EuiDataGrid] Expansion popover needs more customization

[cchaos]

While the expansion popover was originally built purely to be a full view of the cell contents, there is a growing need to make it more complex/custom. Several things that are needed:

• Allow consumers to control the open/closed state [Security Solution]Able to view Hit Enter modal and Inspect icon modal at same time after existing inspect full screen kibana#115339 (resolved by [EuiDataGrid] Allow consuming applications to control various internal state via ref #5590)
• Allow consumers to completely control the popover contents including the custom controls (resolved by [EuiDataGrid] Replace popoverContents API with renderCellPopover #5640)
• Fix the hard-coded high z-index (resolved by [EuiDataGrid] Fix cell popovers overlapping with modals and flyouts #5461)

[cee-chen]

cc @chandlerprall and @thompsongl

Just wanted to get more convo going on this as I think there's some higher level decisions to make here before just yoloing into the code.

1. Allow consumers to control the open/closed state

Do we intend to completely hand over the cell popover state to the consumer (i.e., they're now required to be fully in charge of setting their own isOpen state a la EuiPopover), or do we want to only optionally give them the ability to pass in a true/false but fall back to our own internal state management if the consumer does not opt in?

2. Allow consumers to completely control the popover contents including the custom controls

Just to make sure I'm on the same page - it appears to me that consumers already have complete control over popover contents via the popoverContents API (https://elastic.github.io/eui/#/tabular-content/data-grid-schemas-and-popovers). Is the feature request here then just to allow users to customize the actual popover toggles (aka cell actions)?

Other random thoughts:

• Just to make sure we're thinking ahead, will completely custom cell actions (e.g. an arbitrary ReactNode) potentially conflict at all with the feature request in EuiDataGrid cellAction and expand popover  #5132 (or is that fine/mostly separate)?
• Also maybe worth considering this could solve [EuiDataGrid] Control isExpandable at the cell level #2793 at the same time, which requests the ability to disable cell actions per-cell vs. per-column.

Fix the hard-coded high z-index

Edit: Went ahead and opened a PR for this: #5461

[thompsongl]

Thanks, Constance! I also have some thoughts to get down and discuss, but my other in-progress work has consumed my attention this week. I'll make this a priority next week.

[cee-chen]

No worries at all! The last item (z-index) looks pretty straightforward at second glance so I might go ahead and tackle it and leave all the hard questions to you

[michaelolo24]

Was going through some of the items in our backlog and also noticed this: elastic/kibana#115341 @constancecchen , should the open and close popovers help us handle this as well? Thanks!

[cee-chen]

Yes, it will! You will be able to grab closeCellPopover() from the data grid's ref and manually call it in the same action you use to open your modal or perform a navigation action, etc. You can see https://eui.elastic.co/pr_5550/#/tabular-content/data-grid-ref-methods for an example + demo JS.