main.addon.GoogleMaps: support for advanced markers

[tobiu]

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The default markers API is sadly now deprecated:

The advanced markers API requires a new API key, which is bound to a credit card:

We do need an alternative, since we can no longer just drop a key into the Earthquakes tutorial.

Asking interested devs, who want to learn neo, to get an own key first would create too much of a barrier.

Creating an alternative first has a higher priority, but we need to get this addon functional again anyways.

@maxrahder @gplanansky