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/oracle-apex.json

@@ -1,8 +1,5 @@
 {
   "releases": {
-    "5.1": {
-      "name": "5.1"
-    },
     "24.2": {
       "name": "24.2",
       "eol": "2027-01-31"
@@ -14,39 +11,6 @@
     "23.2": {
       "name": "23.2",
       "eol": "2025-11-30"
-    },
-    "23.1": {
-      "name": "23.1"
-    },
-    "22.2": {
-      "name": "22.2"
-    },
-    "22.1": {
-      "name": "22.1"
-    },
-    "21.2": {
-      "name": "21.2"
-    },
-    "21.1": {
-      "name": "21.1"
-    },
-    "20.2": {
-      "name": "20.2"
-    },
-    "20.1": {
-      "name": "20.1"
-    },
-    "19.2": {
-      "name": "19.2"
-    },
-    "19.1": {
-      "name": "19.1"
-    },
-    "18.2": {
-      "name": "18.2"
-    },
-    "18.1": {
-      "name": "18.1"
     }
   },
   "versions": {}