Error handling: Tweak Reporter interface

Because reporters are used for exceptions we were not able to handle, it
makes sense to simply pass the exception, not the "handled error".

src/Foundation/ErrorHandling/LogReporter.php

@@ -12,6 +12,7 @@
 namespace Flarum\Foundation\ErrorHandling;
 
 use Psr\Log\LoggerInterface;
+use Throwable;
 
 /**
  * Log caught exceptions to a PSR-3 logger instance.
@@ -28,8 +29,8 @@ class LogReporter implements Reporter
         $this->logger = $logger;
     }
 
-    public function report(HandledError $error)
+    public function report(Throwable $error)
     {
-        $this->logger->error($error->getError());
+        $this->logger->error($error);
     }
 }

src/Foundation/ErrorHandling/Reporter.php

@@ -11,7 +11,15 @@
 
 namespace Flarum\Foundation\ErrorHandling;
 
+use Throwable;
+
 interface Reporter
 {
-    public function report(HandledError $error);
+    /**
+     * Report an error that Flarum was not able to handle to a backend.
+     *
+     * @param Throwable $error
+     * @return void
+     */
+    public function report(Throwable $error);
 }