MDL-81522 phpunit: Add a few non-void return types to tests

This is the final (3rd) commit, where we are adding missing
return types to a few tests (using @Depends) which return
types are non-void, but something really returned (for consume
by the dependent test).

lib/filestorage/tests/file_storage_test.php

@@ -209,7 +209,7 @@ public function test_create_file_from_pathname(): void {
      *
      * @covers ::get_file
      */
-    public function test_get_file() {
+    public function test_get_file(): stored_file {
         global $CFG;
 
         $this->resetAfterTest(false);

lib/phpunit/tests/advanced_test.php

@@ -422,7 +422,7 @@ public function test_message_processors_reset(): void {
         $this->assertEquals(count($processors1) + 1, count($processors3));
     }
 
-    public function test_message_redirection() {
+    public function test_message_redirection(): \phpunit_message_sink {
         $this->preventResetByRollback(); // Messaging is not compatible with transactions...
         $this->resetAfterTest(false);
 
@@ -544,7 +544,7 @@ public function test_message_redirection() {
     /**
      * @depends test_message_redirection
      */
-    public function test_message_redirection_noreset($sink): void {
+    public function test_message_redirection_noreset(\phpunit_message_sink $sink): void {
         if ($this->isInIsolation()) {
             $this->markTestSkipped('State cannot be carried over between tests in isolated tests');
         }

lib/tests/navigationlib_test.php

@@ -358,7 +358,7 @@ public function test_module_extends_navigation(): void {
         $this->assertFalse($node->exposed_module_extends_navigation('test1'));
     }
 
-    public function test_navbar_prepend_and_add() {
+    public function test_navbar_prepend_and_add(): \moodle_page {
         global $PAGE;
         // Unfortunate hack needed because people use global $PAGE around the place.
         $PAGE->set_url('/');
@@ -452,7 +452,7 @@ public function test_cache_set(): void {
         $this->assertEquals($cache->software, 'Moodle');
     }
 
-    public function test_setting___construct() {
+    public function test_setting___construct(): settings_navigation {
         global $PAGE, $SITE;
 
         $this->resetAfterTest(false);
@@ -470,7 +470,7 @@ public function test_setting___construct() {
      * @param mixed $node
      * @return mixed
      */
-    public function test_setting__initialise($node) {
+    public function test_setting__initialise($node): settings_navigation {
         $this->resetAfterTest(false);
 
         $node->initialise();