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/envoy.json

@@ -1,23 +1,5 @@
 {
   "releases": {
-    "1.9": {
-      "name": "1.9"
-    },
-    "1.8": {
-      "name": "1.8"
-    },
-    "1.7": {
-      "name": "1.7"
-    },
-    "1.6": {
-      "name": "1.6"
-    },
-    "1.5": {
-      "name": "1.5"
-    },
-    "1.4": {
-      "name": "1.4"
-    },
     "1.34": {
       "name": "1.34",
       "eol": "2026-04-15"
@@ -38,9 +20,6 @@
       "name": "1.30",
       "eol": "2025-04-16"
     },
-    "1.3": {
-      "name": "1.3"
-    },
     "1.29": {
       "name": "1.29",
       "eol": "2025-01-16"
@@ -81,9 +60,6 @@
       "name": "1.20",
       "eol": "2022-10-05"
     },
-    "1.2": {
-      "name": "1.2"
-    },
     "1.19": {
       "name": "1.19",
       "eol": "2022-07-13"
@@ -115,18 +91,6 @@
     "1.12": {
       "name": "1.12",
       "eol": "2020-10-31"
-    },
-    "1.11": {
-      "name": "1.11"
-    },
-    "1.10": {
-      "name": "1.10"
-    },
-    "1.1": {
-      "name": "1.1"
-    },
-    "1.0": {
-      "name": "1.0"
     }
   },
   "versions": {