[Maps] [Embeddables] Enable map zoom with keyboard modifier + scroll

[spong]

Currently scroll to zoom is disabled on embedded maps and maps in dashboards to prevent scroll-hijacking from the map component when the user is scrolling down the page. This is an enhancement request to provide the ability to scroll to zoom while pressing a modifier key, which will continue to prevent the scroll-hijacking issue, but also provide scroll to zoom functionality.

Relevant discussion is available in #7778

A similar implementation can be seen on embedded Google Maps (docs), where a scroll action on a map with no modifier key pressed results in an informational overlay:

[elasticmachine]

Pinging @elastic/kibana-gis