chore(deps): bundle open Renovate PRs and group future updates (#207)

Consolidates #203, #204, #205, #206 into one PR and configures Renovate
to group future updates by ecosystem (npm, gradle, dockerfile) so
there's at most one PR per ecosystem per cycle.

Author: coopernetes

renovate.json

@@ -6,16 +6,19 @@
     {
       "matchManagers": ["npm"],
       "matchFileNames": ["git-proxy-java-dashboard/frontend/package.json"],
-      "labels": ["dependencies", "frontend"]
+      "labels": ["dependencies", "frontend"],
+      "groupName": "frontend npm dependencies"
     },
     {
       "matchManagers": ["gradle", "gradle-wrapper"],
-      "labels": ["dependencies", "java"]
+      "labels": ["dependencies", "java"],
+      "groupName": "java dependencies"
     },
     {
       "matchManagers": ["dockerfile"],
       "labels": ["dependencies", "docker"],
-      "pinDigests": true
+      "pinDigests": true,
+      "groupName": "docker dependencies"
     },
     {
       "matchDepTypes": ["devDependencies"],