Fixes and QoL changes for the "Strait of Malacca" map (#3914)

## Description:

Fixes:
 
Various rivers with pixel-gap errors, that made players and ships unable
to boat out of the river into the sea. This error was reported in the
Discord server
 
<img width="876" height="481" alt="image"
src="https://github.com/user-attachments/assets/9afb31f9-f5a9-4792-bd44-3ea18fe21777"
/>


Also changes:

- Better Terrain (old version had no brown terrain and smidges of white
terrain, which made almost all the map practically green terrain). The
coastlines and terrain area remain the exact same ( the small land
change in manifest was because the old map had little random pixel lakes
all around)

- More Nations (NPCs) , more consistent names for them, and an extra
flag (Aceh)

## 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:

tri.star1011

map-generator/assets/maps/straitofmalacca/info.json

@@ -1,5 +1,5 @@
 {
-  "name": "straitofmalacca",
+  "name": "Strait Of Malacca",
   "nations": [
     {
       "coordinates": [1268, 730],
@@ -11,40 +11,60 @@
       "name": "Thailand",
       "flag": "th"
     },
-    {
-      "coordinates": [1328, 1284],
-      "name": "Sumatra",
-      "flag": "id"
-    },
-    {
-      "coordinates": [1141, 1090],
-      "name": "Burmese Pythons",
-      "flag": "mm"
-    },
     {
       "coordinates": [210, 243],
       "name": "Aceh",
-      "flag": "id"
-    },
-    {
-      "coordinates": [1011, 736],
-      "name": "Riau",
-      "flag": "id"
-    },
-    {
-      "coordinates": [600, 565],
-      "name": "Samosir",
-      "flag": "id"
-    },
-    {
-      "coordinates": [827, 999],
-      "name": "Barisan",
-      "flag": "id"
+      "flag": "Aceh"
     },
     {
       "coordinates": [1053, 333],
       "name": "Malaysia",
       "flag": "my"
+    },
+    {
+      "coordinates": [596, 573],
+      "name": "North Sumatra",
+      "flag": "id"
+    },
+    {
+      "coordinates": [797, 1002],
+      "name": "West Sumatra",
+      "flag": "id"
+    },
+    {
+      "coordinates": [956, 743],
+      "name": "Riau",
+      "flag": "id"
+    },
+    {
+      "coordinates": [1644, 1265],
+      "name": "Bangka Belitung",
+      "flag": "id"
+    },
+    {
+      "coordinates": [1419, 1636],
+      "name": "Lampung",
+      "flag": "id"
+    },
+    {
+      "coordinates": [1084, 1414],
+      "name": "Bengkulu",
+      "flag": "id"
+    },
+    {
+      "coordinates": [1366, 1303],
+      "name": "South Sumatra",
+      "flag": "id"
+    },
+    {
+      "coordinates": [1167, 1071],
+      "name": "Jambi",
+      "flag": "id"
+    },
+    {
+      "coordinates": [1383, 938],
+      "name": "Riau Islands",
+      "flag": "id"
     }
   ]
 }