Add a select all flow runs checkbox to the flow runs page.

[collincchoy]

This PR adds the ability to select all flow runs in the current view on the flow runs page to more easily enable deleting multiple flow runs.

Note: Because the flow runs list is virtualized, when filtering for 200+ flow runs, selecting all will only select what's currently in view

	📸 Screenshots
Select all
Deselect all

Example

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