Test file_cache prime shm + use file combination

We're currently only testing prime shm + use shm and prime file +
use file.

This adds testing for the prime shm + use file combination. The
prime file + use shm combination is broken on PHP-8.0, so not
tested.

Author: nikic

azure/file_cache_job.yml

@@ -21,19 +21,28 @@ jobs:
     - template: test.yml
       parameters:
         configurationName: ${{ parameters.configurationName }}
-        runTestsName: 'File Cache (prime)'
+        runTestsName: 'File Cache (prime shm)'
         runTestsParameters: >-
           ${{ parameters.runTestsParameters }}
           -d zend_extension=opcache.so
           --file-cache-prime
     - template: test.yml
       parameters:
         configurationName: ${{ parameters.configurationName }}
-        runTestsName: 'File Cache (use)'
+        runTestsName: 'File Cache (prime shm, use shm)'
         runTestsParameters: >-
           ${{ parameters.runTestsParameters }}
           -d zend_extension=opcache.so
           --file-cache-use
+    - template: test.yml
+      parameters:
+        configurationName: ${{ parameters.configurationName }}
+        runTestsName: 'File Cache (prime shm, use file)'
+        runTestsParameters: >-
+          ${{ parameters.runTestsParameters }}
+          -d zend_extension=opcache.so
+          --file-cache-use
+          -d opcache.file_cache_only=1
     - template: test.yml
       parameters:
         configurationName: ${{ parameters.configurationName }}