Add 8-trixie and 8-bookworm variants to java and java-postgres templates

Added Java 8 variants (8-trixie, 8-bookworm) to both java and java-postgres
devcontainer-template.json proposals. Tags verified against MCR.

Co-authored-by: Kaniska244 <186041440+Kaniska244@users.noreply.github.com>

Author: Copilot

src/java-postgres/devcontainer-template.json

@@ -15,10 +15,12 @@
                 "21-trixie",
                 "17-trixie",
                 "11-trixie",
+                "8-trixie",
                 "25-bookworm",
                 "21-bookworm",
                 "17-bookworm",
-                "11-bookworm"
+                "11-bookworm",
+                "8-bookworm"
             ],
             "default": "25-trixie"
         },

src/java/devcontainer-template.json

@@ -15,10 +15,12 @@
                 "21-trixie",
                 "17-trixie",
                 "11-trixie",
+                "8-trixie",
                 "25-bookworm",
                 "21-bookworm",
                 "17-bookworm",
-                "11-bookworm"
+                "11-bookworm",
+                "8-bookworm"
             ],
             "default": "25-trixie"
         },