feat: Add rebrand CI/CD workflows to main branch

- Add 72 rebrand workflow files (polkadot→pezkuwi, substrate→bizinikiwi, cumulus→pezcumulus)
- Add GitHub actions, issue templates, and configs
- Removed unnecessary workflows (fork-sync, gitspiegel, upstream-tracker, sync-templates, backport)
- Renamed zombienet test files to match new naming convention

.github/ISSUE_TEMPLATE/config.yml

@@ -0,0 +1,7 @@
+blank_issues_enabled: true
+contact_links:
+  - name: Support & Troubleshooting with the Bizinikiwi Stack Exchange Community
+    url: https://exchange.pezkuwichain.app
+    about: |
+      For general problems with Bizinikiwi or related technologies, please search here first
+      for solutions, by keyword and tags. If you discover no solution, please then ask and questions in our community! We highly encourage everyone also share their understanding by answering questions for others.