Add contextmenu for map-extent layercontrol

[AliyanH]

Closes #926

• [X] Add "Zoom to Sub Layer" + "Copy Sub Layer"
• [X] Add support for keyboard navigation
• [X] Add support for Keyboard shortcut
• [x] Add localization
• [x] Add missing localization for "Sub-Layer"
• [ ] ~Re-key copy layer/extent shortcut from 'L' to 'C'?~
• [x] when layer control context menu is open DO NOT collapse layer control?
• [x] Add tests

Future work

• Abiltiy to paste map-extent into layers?

[AliyanH]

Thanks @prushforth! Will merge after finalizing https://github.com/Maps4HTML/mapml-extension/pull/69

[prushforth]

Thanks @prushforth! Will merge after finalizing Maps4HTML/mapml-extension#69

We should merge this when it's ready so that we can release it as 0.13.1 (with a small other GeoServer-related change that wouldn't pass CI reliably without these commits) with GeoServer 2.25.0, which will happen March 18th. I could merge that change without this, of course, but it was easier to rebase it on the work done in this branch which eliminates some test flakiness (there's always a new source of flakiness, for some reason).

The GeoServer viewer should not depend on the extension, but I agree the extension needs this update.

I will open a GeoServer PR this week to include the new viewer, which we can update until Friday.

[prushforth]

I'll cut a 0.13.1 release later today, hopefully in time to make the GeoServer 2.25.0 release cut-off, tbd.