ci: add Dependabot groups (#1553)

## Description

This PR introduces [dependabot PR
grouping](https://docs.github.com/en/code-security/dependabot/dependabot-version-updates/configuration-options-for-the-dependabot.yml-file#groups),
based on historical single PRs in the repo.

<details><summary>Contributors' checklist...</summary>

- [x] Added new tests, or not needed, or not feasible
- [x] Provided an example (e.g. screenshot) to aid review or the PR is
self-explanatory
- [x] Updated the official documentation or not needed
- [x] No breaking changes were made, or a `BREAKING CHANGE: xxx` message
was included in the description
- [ ] Added references to related issues and PRs
- [ ] Provided any useful hints for running manual tests
- [ ] Added new benchmarks to [generated
graphs](https://gnoland.github.io/benchmarks), if any. More info
[here](https://github.com/gnolang/gno/blob/master/.benchmarks/README.md).
</details>

.github/dependabot.yml

@@ -17,6 +17,18 @@ updates:
       interval: weekly
     labels:
       - "dependencies"
+    groups:
+      golang-x:
+        patterns:
+          - "golang.org/x/*"
+      dbs:
+        patterns:
+          - "github.com/linxGnu/grocksdb"
+          - "go.etcd.io/bbolt"
+          - "github.com/dgraph-io/badger/v3"
+      everything-else:
+        patterns:
+          - "*"
     open-pull-requests-limit: 10
     pull-request-branch-name:
       separator: "-"