Internal issue 2937 - IcPopoverMenu - Allow users to supply popper properties

The IcPopoverMenu component uses the PopperJS library. This library has a lot of customisation options and modifiers; currently though they are hard coded within the IC-UI-Kit.

One such modifier would be to allow users to define the RootBoundary; currently it is hard coded to the entire viewport, but users could make use from setting it to be the containing element.

Another would be to allow the user to define a list of fallback placements for the Popover. Currently this is coded (in order) as \["top-start", "top-end", "bottom-end"]. Allowing users to specify a custom ordering for this would allow for greater versatility of the IcPopoverMenu.

Start by locating the IcPopoverMenu component and reviewing how its PopperJS properties are currently configured. Define how users should supply the root boundary and fallback placement order, then verify that both options override the current hard-coded behavior without changing the defaults.

Written by the indexing model from the issue text.