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/bamboo.json

@@ -12,27 +12,6 @@
       "name": "9.4",
       "eol": "2025-10-26"
     },
-    "9.3": {
-      "name": "9.3"
-    },
-    "9.2": {
-      "name": "9.2"
-    },
-    "9.1": {
-      "name": "9.1"
-    },
-    "9.0": {
-      "name": "9.0"
-    },
-    "8.2": {
-      "name": "8.2"
-    },
-    "8.1": {
-      "name": "8.1"
-    },
-    "8.0": {
-      "name": "8.0"
-    },
     "11.0": {
       "name": "11.0",
       "eol": "2027-04-30"