Implement v2 styles endpoint and update layer inheritance

[gowin20]

Implements #150 #174 #170

#150 - Change VectorBasemapLayer to inherit from VectorTileLayer

• VectorBasemapLayer now inherits onAdd and _createMaplibreLayer from VectorTileLayer, and performs a super call to the VectorTileLayer constructor.
• Some functions remain unmerged, such as onRemove and _asyncAdd, due to the dynamic data attribution in VectorBasemapLayer

#174 - add support for the v2 basemap styles service

(see #175)

• Added new getBasemapStyleV2Url function that returns a formatted reference to the new v2 endpoint
• New version parameter in VectorBasemapLayer that specifies the endpoint to access (1 or 2) If not provided, the version will attempt to set itself based on the provided style enumeration
• New language parameter that works with v2 of the service, accepts valid language parameters

#170 - fix default pane for VectorBasemapLayer

(see #181)

• Fixed a bug where VectorBasemapLayer was not being added to the tilePane
• Added additional code to create a new esri-details pane for styles of type :Details//details
• Changed default z-index of esri-labels pane to display below the overlayPane
• Added unit tests

[gavinr]

Overall seems to work for me. A few small things:

[gavinr]

I don't see a unit test for the new functionality "it should load a v2 basemap if using a v2 basemap key enum even if not passing the version: 2 property" - can you add a unit test for that case?

[patrickarlt]

LGTM! Minor code suggestion but please add the test that @gavinr has indicated.

[gavinr]

Released in v4.1.0.