bug symfony#61234 [Cache] RedisTrait::doFetch should use pipeline with GET's instead of MGET for Relay\Cluster (dorrogeray)

This PR was submitted for the 7.3 branch but it was merged into the 6.4 branch instead.

Discussion
----------

[Cache] RedisTrait::doFetch should use pipeline with GET's instead of MGET for Relay\Cluster

| Q             | A
| ------------- | ---
| Branch?       | 6.4
| Bug fix?      | yes
| New feature?  | no
| Deprecations? | no
| Issues        | Fix #...
| License       | MIT

🛠️ `Relay\Cluster` should be expected to operate with >1 master nodes, and therefore its not safe to use `mget` when fetching the ids in `RedisTrait::doFetch(array $ids)` as they are not guaranteed to be on a same hash slot.

This change makes `doFetch` use pipeline with `GET` commands when `$this->redis instanceof RelayCluster`

Commits
-------

30a2ca0 [cache] RedisTrait::doFetch should use pipeline instead of mget for Relay\Cluster

Author: nicolas-grekas

src/Symfony/Component/Cache/Traits/RedisTrait.php

@@ -434,7 +434,7 @@ protected function doFetch(array $ids): iterable
 
         $result = [];
 
-        if ($this->redis instanceof \Predis\ClientInterface && ($this->redis->getConnection() instanceof ClusterInterface || $this->redis->getConnection() instanceof Predis2ClusterInterface)) {
+        if (($this->redis instanceof \Predis\ClientInterface && ($this->redis->getConnection() instanceof ClusterInterface || $this->redis->getConnection() instanceof Predis2ClusterInterface)) || $this->redis instanceof RelayCluster) {
             $values = $this->pipeline(function () use ($ids) {
                 foreach ($ids as $id) {
                     yield 'get' => [$id];