Add support for parsing MLT-format vector tile sources (#3246)

Co-authored-by: Bart Louwers <bart@emeel.net>
Co-authored-by: Bart Louwers <bart.louwers@gmail.com>

metrics/integration/render-tests/extent/1024-symbol/style.json

@@ -2,7 +2,13 @@
   "version": 8,
   "metadata": {
     "test": {
-      "allowed": 0.003
+      "allowed": 0.003,
+      "source-replace": [
+        {
+          "replace": "maplibre",
+          "with": "mlt"
+        }
+      ]
     }
   },
   "center": [
@@ -19,6 +25,14 @@
       "tiles": [
         "local://tiles/extent1024-14-8802-5374.mvt"
       ]
+    },
+    "mlt": {
+      "type": "vector",
+      "maxzoom": 14,
+      "tiles": [
+        "local://tiles/extent1024-14-8802-5374.mlt"
+      ],
+      "encoding": "mlt"
     }
   },
   "layers": [

metrics/integration/render-tests/fill-pattern/wrapping-with-interpolation/style.json

@@ -1,7 +1,14 @@
 {
   "version": 8,
   "metadata": {
-    "test": {}
+    "test": {
+      "source-replace": [
+        {
+          "replace": "maplibre",
+          "with": "mlt"
+        }
+      ]
+    }
   },
   "zoom": 0.99,
   "center": [
@@ -15,6 +22,14 @@
       "tiles": [
         "local://tiles/{z}-{x}-{y}.mvt"
       ]
+    },
+    "mlt": {
+      "type": "vector",
+      "maxzoom": 14,
+      "tiles": [
+        "local://tiles/{z}-{x}-{y}.mlt"
+      ],
+      "encoding": "mlt"
     }
   },
   "sprite": "local://sprites/solid-black",

metrics/integration/render-tests/icon-visibility/visible/style.json

@@ -2,7 +2,11 @@
   "version": 8,
   "metadata": {
     "test": {
-      "height": 256
+      "height": 256,
+      "source-replace": [{
+          "replace": "maplibre",
+          "with": "mlt"
+      }]
     }
   },
   "center": [
@@ -17,6 +21,14 @@
       "tiles": [
         "local://tiles/{z}-{x}-{y}.mvt"
       ]
+    },
+    "mlt": {
+      "type": "vector",
+      "maxzoom": 14,
+      "tiles": [
+        "local://tiles/{z}-{x}-{y}.mlt"
+      ],
+      "encoding": "mlt"
     }
   },
   "sprite": "local://sprites/sprite",

metrics/integration/render-tests/text-pitch-alignment/viewport-overzoomed-single-glyph/style.json

@@ -1,5 +1,15 @@
 {
   "version": 8,
+  "metadata": {
+    "test": {
+      "source-replace": [
+        {
+          "replace": "maplibre",
+          "with": "mlt"
+        }
+      ]
+    }
+  },
   "center": [
     -118.28162,
     33.86852
@@ -14,6 +24,14 @@
       "tiles": [
         "local://tiles/mapbox.mapbox-streets-v7/16-11235-26208.mvt"
       ]
+    },
+    "mlt": {
+      "type": "vector",
+      "maxzoom": 16,
+      "tiles": [
+        "local://tiles/mapbox.mapbox-streets-v7/16-11235-26208.mlt"
+      ],
+      "encoding": "mlt"
     }
   },
   "glyphs": "local://glyphs/{fontstack}/{range}.pbf",

metrics/integration/render-tests/tms/tms/style.json

@@ -1,7 +1,14 @@
 {
   "version": 8,
   "metadata": {
-    "test": {}
+    "test": {
+      "source-replace": [
+        {
+          "replace": "maplibre",
+          "with": "mlt"
+        }
+      ]
+    }
   },
   "zoom": 2,
   "sources": {
@@ -12,6 +19,15 @@
       "tiles": [
         "local://tiles/{z}-{x}-{y}.tms.mvt"
       ]
+    },
+    "mlt": {
+      "type": "vector",
+      "maxzoom": 14,
+      "scheme": "tms",
+      "tiles": [
+        "local://tiles/{z}-{x}-{y}.tms.mlt"
+      ],
+      "encoding": "mlt"
     }
   },
   "layers": [