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/mariadb.json

@@ -30,42 +30,12 @@
       "eol": "2028-06-04",
       "eoes": "2033-10-15"
     },
-    "11.7": {
-      "name": "11.7"
-    },
-    "11.6": {
-      "name": "11.6"
-    },
-    "11.5": {
-      "name": "11.5"
-    },
     "11.4": {
       "name": "11.4",
       "releaseDate": "2024-05-29",
       "eol": "2029-05-29",
       "eoes": "2033-01-16"
     },
-    "11.3": {
-      "name": "11.3"
-    },
-    "11.2": {
-      "name": "11.2"
-    },
-    "11.1": {
-      "name": "11.1"
-    },
-    "11.0": {
-      "name": "11.0"
-    },
-    "10.9": {
-      "name": "10.9"
-    },
-    "10.8": {
-      "name": "10.8"
-    },
-    "10.7": {
-      "name": "10.7"
-    },
     "10.6": {
       "name": "10.6",
       "releaseDate": "2021-07-06",
@@ -102,9 +72,6 @@
       "eol": "2028-02-16",
       "eoes": "2028-02-16"
     },
-    "10.10": {
-      "name": "10.10"
-    },
     "10.1": {
       "name": "10.1",
       "releaseDate": "2015-10-17",