MDL-72312 GHA: Force use of igbinary working version

And also remove memcached and redis that have dependencies on it.

Versions 3.2.2 - 3.2.4 have a bug returning
arrays with index messed up. This affects
key() and next() operations when reading
information serialised with igbinary.

Notably Moodle's MUC uses igbinary when
available and was leading to some wrong
operations and test failures.

Once a fixed version is used by GHA this
can be reverted. See MDL-72399.

Note this only affects to php72, newer php
versions are not affected.

.github/workflows/push.yml

@@ -55,9 +55,16 @@ jobs:
         include:
           - os: ubuntu-18.04
             php: 7.2
+            # Need to disable both redis and memcached (both are optional) in order to keep igbinary installed.
+            # (there are dependencies that become broken if we just switch the igbinary version).
+            # Need to do this for php 7.2 because of a bug with current default igbinary
+            # versions used by GHA being >= 3.2.2 and <= 3.2.4 (buggy ones).
+            # TODO: MDL-72399 - Revert this patch once igbinary 3.2.5 or up is the default @ GHA.
+            extensions: :redis, :memcached, igbinary-3.2.6
             db: mysqli
           - os: ubuntu-18.04
             php: 7.4
+            extensions:
             db: pgsql
 
     steps:
@@ -88,6 +95,7 @@ jobs:
         uses: shivammathur/setup-php@v2
         with:
           php-version: ${{ matrix.php }}
+          extensions: ${{ matrix.extensions }}
           coverage: none
 
       - name: Checking out code from ${{ env.GITHUB_REF_SLUG }}