Add custom tree for placing area markers

[mharis001]

When merged this pull request will:

• Add a custom markers tree for placing area markers
  • Like 3DEN, where markers mode has two sub-modes (icons and areas)
  • Placement works the same as placing any other entity through Zeus (only on map though)
• Remove module and context menu action for placing area markers
• Move handling of tree buttons in editor component to script and emit an event when they are clicked for easier expansion by other components
• Remove side buttons fix - not needed anymore, fixed by base game
• Add execAfterNFrames common function - convenient wrapper for many stacked CBA_fnc_execNextFrame calls

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