Move map generator into main repo (#2006)

## Description:

Move the MapGenerator repo into OpenFrontIO so we don't need to copy
generated map files over.

## Please complete the following:

- [x] I have added screenshots for all UI updates
- [x] I process any text displayed to the user through translateText()
and I've added it to the en.json file
- [x] I have added relevant tests to the test directory
- [x] I confirm I have thoroughly tested these changes and take full
responsibility for any bugs introduced

## Please put your Discord username so you can be contacted if a bug or
regression is found:

evan

tests/testdata/maps/half_land_half_ocean/manifest.json

@@ -1,12 +1,12 @@
 {
   "map": {
     "height": 16,
-    "num_land_tiles": 160,
+    "num_land_tiles": 128,
     "width": 16
   },
   "mini_map": {
     "height": 8,
-    "num_land_tiles": 48,
+    "num_land_tiles": 32,
     "width": 8
   },
   "name": "Half Land Half Ocean"

tests/testdata/maps/ocean_and_land/manifest.json

@@ -1,12 +1,12 @@
 {
   "map": {
     "height": 16,
-    "num_land_tiles": 178,
+    "num_land_tiles": 134,
     "width": 16
   },
   "mini_map": {
     "height": 8,
-    "num_land_tiles": 50,
+    "num_land_tiles": 33,
     "width": 8
   },
   "name": "Ocean and Land"