feat: GitHub Issues Consolidation (#517)

This pull request updates the issue reporting process by removing the
local bug and feature request templates and directing users to a
centralized repository for all Azure Landing Zones (ALZ) issues. It also
updates the configuration to prevent blank issues and provides a contact
link to the new centralized location.

**Issue template and triage process changes:**

* Removed `.github/ISSUE_TEMPLATE/bug_report.yml` and
`.github/ISSUE_TEMPLATE/feature_request.yml` to eliminate local bug and
feature request templates, encouraging users to use the centralized
issue tracking system instead.
[[1]](diffhunk://#diff-637f7b97bba458badb691a1557c3d4648686292e948dbe3e8360564378b653efL1-L110)
[[2]](diffhunk://#diff-c6b098646bf32c644234bec14c2675ea2a3d9c2dc2df450a25aa0e7ff02323cdL1-L68)
* Updated `.github/ISSUE_TEMPLATE/config.yml` to disable blank issues
and added a `contact_links` entry that directs users to the centralized
ALZ issues repository for all bugs, features, and questions.

Author: jtracey93

.github/ISSUE_TEMPLATE/bug_report.yml

@@ -1,2 +1,5 @@
----
 blank_issues_enabled: false
+contact_links:
+  - name: ALZ bugs / features / questions (everything goes here)
+    url: https://github.com/Azure/Azure-Landing-Zones/issues/new/choose
+    about: Centralized repo for all Azure landing zone (ALZ) bugs, features, and questions (new for 2026)