Add raxflex provider and debian-bullseye image

This adds the initial nodepool-in-zuul config to:

* Tell zuul that it's responsible for an image named "debian-bullseye"
* Attach the job to a pipeline that builds missing images
* Connect to raxflex and upload that image
* Use that image when launching nodes with a label of
  "niz-debian-bullseye-normal"

Change-Id: I8a838253a4683f34f538c90949369ba2d192e8d7

zuul.d/flavors.yaml

@@ -0,0 +1,2 @@
+- flavor:
+    name: normal

zuul.d/images.yaml

@@ -0,0 +1,3 @@
+- image:
+    name: debian-bullseye
+    type: zuul

zuul.d/labels.yaml

@@ -0,0 +1,7 @@
+# During testing, prefix all label names with "niz-" so it's very
+# clear which system we're using.
+
+- label:
+    name: niz-debian-bullseye-normal
+    image: debian-bullseye
+    flavor: normal

zuul.d/project.yaml

@@ -9,3 +9,10 @@
               - name: image_upload_secret
                 secret: image-upload-secret
                 pass-to-parent: true
+    image-build:
+      jobs:
+        - opendev-build-diskimage-debian-bullseye:
+            secrets:
+              - name: image_upload_secret
+                secret: image-upload-secret
+                pass-to-parent: true

zuul.d/providers.yaml

@@ -0,0 +1,23 @@
+- section:
+    name: raxflex-base
+    abstract: true
+    connection: raxflex
+    boot-timeout: 120
+    launch-timeout: 600
+    flavors:
+      - name: normal
+        flavor-name: gp.0.4.8
+    images:
+      - name: debian-bullseye
+
+- section:
+    name: raxflex-sjc3
+    parent: raxflex-base
+    region: SJC3
+
+- provider:
+    name: raxflex-sjc3-main
+    section: raxflex-sjc3
+    labels:
+      - name: niz-debian-bullseye-normal
+        key-name: infra-root-keys-2024-04-08