fix(shuffle-tests): Update the shuffle-test backend-test job definition to match definition in backend.yml (#82327)

<!-- Describe your PR here. -->
Shuffle tests are failing due to lower shard count and missing service
dependencies. Sync the backend-test job with the definition in
backend.yml
<!--

  Sentry employees and contractors can delete or ignore the following.

-->

### Legal Boilerplate

Look, I get it. The entity doing business as "Sentry" was incorporated
in the State of Delaware in 2015 as Functional Software, Inc. and is
gonna need some rights from me in order to utilize my contributions in
this here PR. So here's the deal: I retain all rights, title and
interest in and to my contributions, and by keeping this boilerplate
intact I confirm that Sentry can use, modify, copy, and redistribute my
contributions, under Sentry's choice of terms.

.github/workflows/shuffle-tests.yml

@@ -28,18 +28,22 @@ jobs:
     name: run backend tests
     runs-on: ubuntu-24.04
     timeout-minutes: 90
+    permissions:
+      contents: read
+      id-token: write
     strategy:
       # This helps not having to run multiple jobs because one fails, thus, reducing resource usage
       # and reducing the risk that one of many runs would turn red again (read: intermittent tests)
       fail-fast: false
       matrix:
         # XXX: When updating this, make sure you also update MATRIX_INSTANCE_TOTAL.
-        instance: [0, 1, 2, 3, 4, 5, 6]
+        instance: [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
         pg-version: ['14']
 
     env:
-      # XXX: MATRIX_INSTANCE_TOTAL must be hardcoded to the length of strategy.matrix.instance.
-      MATRIX_INSTANCE_TOTAL: 7
+      # XXX: `MATRIX_INSTANCE_TOTAL` must be hardcoded to the length of `strategy.matrix.instance`.
+      # If this increases, make sure to also increase `flags.backend.after_n_builds` in `codecov.yml`.
+      MATRIX_INSTANCE_TOTAL: 11
 
     steps:
       - uses: actions/checkout@692973e3d937129bcbf40652eb9f2f61becf3332 # v4.1.7
@@ -48,7 +52,10 @@ jobs:
         uses: ./.github/actions/setup-sentry
         id: setup
         with:
+          redis_cluster: true
+          kafka: true
           snuba: true
+          symbolicator: true
           # Right now, we run so few bigtable related tests that the
           # overhead of running bigtable in all backend tests
           # is way smaller than the time it would take to run in its own job.