Remove invalid releases automatically (#466)

Automatically remove empty releases or releases which are released in the future, regardless of the product.

Also refactored a bit releasedata.py to use better names and clarify types.

releases/angular.json

@@ -1,8 +1,5 @@
 {
   "releases": {
-    "9": {
-      "name": "9"
-    },
     "20": {
       "name": "20",
       "releaseDate": "2025-05-28",
@@ -20,30 +17,6 @@
       "releaseDate": "2024-05-22",
       "eoas": "2024-11-19",
       "eol": "2025-11-21"
-    },
-    "17": {
-      "name": "17"
-    },
-    "16": {
-      "name": "16"
-    },
-    "15": {
-      "name": "15"
-    },
-    "14": {
-      "name": "14"
-    },
-    "13": {
-      "name": "13"
-    },
-    "12": {
-      "name": "12"
-    },
-    "11": {
-      "name": "11"
-    },
-    "10": {
-      "name": "10"
     }
   },
   "versions": {