.github: add bug_report form to submit Cilium bugs

Instead of a bug template we can start using a bug_report form from
GitHub. This will hopefully guarantee that users will provide the
required information to help us understanding the reported bug.

Signed-off-by: André Martins <andre@cilium.io>

.github/ISSUE_TEMPLATE/bug_report.yaml

@@ -0,0 +1,83 @@
+name: Bug Report
+description: Report a bug encountered while operating Cilium
+labels: ["kind/bug", "needs/triage"]
+body:
+  - type: markdown
+    attributes:
+      value: |
+        Thanks for taking the time to fill out this bug report! If you have usage questions, please try the [slack channel](http://slack.cilium.io/) and see the [FAQ](https://github.com/cilium/cilium/issues?utf8=%E2%9C%93&q=is:issue+label:kind/question+) first.
+
+        **Important**: For security related issues: We strongly encourage you to report security vulnerabilities to the private security mailing list: security@cilium.io - first, before disclosing them in any public forums.
+  - type: checkboxes
+    attributes:
+      label: Is there an existing issue for this?
+      description: Please search to see if an issue already exists for the bug you encountered.
+      options:
+      - label: I have searched the existing issues
+        required: true
+  - type: textarea
+    id: what-happened
+    attributes:
+      label: What happened?
+      description: Also tell us, what did you expect to happen?
+      placeholder: |
+        1. In this environment...
+        2. With this config...
+        3. Run '...'
+        4. See error...
+      value: "A bug happened!"
+    validations:
+      required: true
+  - type: textarea
+    id: cilium-version
+    attributes:
+      label: Cilium Version
+      description: What version of the software was running when you discovered this issue? (run `cilium version`)
+    validations:
+      required: true
+  - type: textarea
+    id: kernel-version
+    attributes:
+      label: Kernel Version
+      description: Which kernel version was Cilium running on? (run `uname -a`)
+    validations:
+      required: true
+  - type: textarea
+    id: k8s-version
+    attributes:
+      label: Kubernetes Version
+      description: Which Kubernetes version are you running? (run `kubectl version`)
+    validations:
+      required: true
+  - type: textarea
+    id: sysdump
+    attributes:
+      label: Sysdump
+      description: |
+        - [Install Cilium CLI](https://docs.cilium.io/en/stable/gettingstarted/k8s-install-default/#install-the-cilium-cli).
+        - Run `cilium sysdump` command
+      placeholder: |
+        Upload the sysdump file here
+  - type: textarea
+    id: logs
+    attributes:
+      label: Relevant log output
+      description: Please copy and paste any relevant log output. This will be automatically formatted into code, so no need for backticks.
+      render: shell
+  - type: textarea
+    attributes:
+      label: Anything else?
+      description: |
+        Links? References? Anything that will provide more context about the issue you are encountering!
+
+        Tip: You can attach images or log files by clicking this area to highlight it and then dragging files in.
+    validations:
+      required: false
+  - type: checkboxes
+    id: terms
+    attributes:
+      label: Code of Conduct
+      description: By submitting this issue, you agree to follow our [Code of Conduct](https://github.com/cilium/cilium/blob/master/CODE_OF_CONDUCT.md)
+      options:
+        - label: I agree to follow this project's Code of Conduct
+          required: true