Updates to ErrorHandler, add missing type hint \Throwable (#18302)

* Updated phpdoc so it has \Throwable

- `abstract protected function renderException($exception);` is extended in web/ErrorHandler to also have `\Error`.
- `public static function convertExceptionToError($exception)` is called from widgets/ActiveField.php with 
```
/**
     * PHP magic method that returns the string representation of this object.
     * @return string the string representation of this object.
     */
    public function __toString()
    {
        // __toString cannot throw exception
        // use trigger_error to bypass this limitation
        try {
            return $this->render();
        } catch (\Exception $e) {
            ErrorHandler::convertExceptionToError($e);
            return '';
        } catch (\Throwable $e) {
            ErrorHandler::convertExceptionToError($e);
            return '';
        }
    }
```

* Add \Throwable to phpdoc in response.php 

The ErrorHandler has been updated in phpdoc to have throwable, this complets that change.

* Update ErrorHandler.php

fixed missing `|`

framework/base/ErrorHandler.php

@@ -298,7 +298,7 @@ abstract class ErrorHandler extends Component
 
     /**
      * Renders the exception.
-     * @param \Exception $exception the exception to be rendered.
+     * @param \Exception|\Error|\Throwable $exception the exception to be rendered.
      */
     abstract protected function renderException($exception);
 
@@ -336,7 +336,7 @@ abstract class ErrorHandler extends Component
      *
      * This method can be used to convert exceptions inside of methods like `__toString()`
      * to PHP errors because exceptions cannot be thrown inside of them.
-     * @param \Exception $exception the exception to convert to a PHP error.
+     * @param \Exception|\Throwable $exception the exception to convert to a PHP error.
      */
     public static function convertExceptionToError($exception)
     {
@@ -345,7 +345,7 @@ abstract class ErrorHandler extends Component
 
     /**
      * Converts an exception into a simple string.
-     * @param \Exception|\Error $exception the exception being converted
+     * @param \Exception|\Error|\Throwable  $exception the exception being converted
      * @return string the string representation of the exception.
      */
     public static function convertExceptionToString($exception)
@@ -363,7 +363,7 @@ abstract class ErrorHandler extends Component
 
     /**
      * Converts an exception into a string that has verbose information about the exception and its trace.
-     * @param \Exception|\Error $exception the exception being converted
+     * @param \Exception|\Error|\Throwable  $exception the exception being converted
      * @return string the string representation of the exception.
      *
      * @since 2.0.14

framework/web/Response.php

@@ -295,7 +295,7 @@ class Response extends \yii\base\Response
 
     /**
      * Sets the response status code based on the exception.
-     * @param \Exception|\Error $e the exception object.
+     * @param \Exception|\Error|\Throwable $e the exception object.
      * @throws InvalidArgumentException if the status code is invalid.
      * @return $this the response object itself
      * @since 2.0.12