#8334 Review mapType configuration and docs

[allyoucanmap]

Description

The PR #8990 introduced the new configuration of mapType but it does not take into account the default visualization mode that for some custom downstream project could be needed (eg initialize the app only in 3D)

New proposed configuration for mapType is:

{
  // allow to define the default visualization mode of the app and
  // which 2D or 3D map library should be used based on the device
  // the configuration below is the default one
  // note: this configuration does not support expressions
  "mapType": {
    // the default visualization mode of the app, it could be "2D" or "3D"
    "defaultVisualizationMode": "2D",
    // map library to use based on the visualization mode and device
    // structure -> { visualizationModes: { [visualizationMode]: { [deviceType]: mapLibrary } } }
    "visualizationModes": {
      "2D": {
        "desktop": "openlayers",
        "mobile": "leaflet"
      },
      "3D": {
        "desktop": "cesium",
        "mobile": "cesium"
      }
    }
  },
}

Please check if the PR fulfills these requirements

• The commit message follows our guidelines: https:/geosolutions-it/MapStore2/blob/master/CONTRIBUTING.md
• Tests for the changes have been added (for bug fixes / features)
• Docs have been added / updated (for bug fixes / features)

What kind of change does this PR introduce? (check one with "x", remove the others)

• Minor changes to existing features

Issue

What is the current behavior?

#8334

What is the new behavior?

Review of new mapType configuration

Breaking change

Does this PR introduce a breaking change? (check one with "x", remove the other)

• Yes, and I documented them in migration notes

Other useful information

[offtherailz]

See only my comment about migration guidelines.

[allyoucanmap]

@ElenaGallo please test this fix on dev as part of the work done in the PR #8990, thanks