Generate valid phpdoc param tags (#1457)

* Fix the phpdoc of the RequestContext

* Generate valid phpdoc param tags

When an array shape key starts with a `@` like `@region`, it must be
quoted in the phpdoc as the unquoted one would be interpreted as the
next phpdoc tag.

* Use an unsealed shape for the type in Input

This avoids reports about passing extra keys from child classes in
Psalm.

* Allow passing null as the region in the input

The base input class already accept null values in addition to omitted
values for the region.

* Update the psalm baseline

* Disallow invalid docblocks in Psalm as well

Author: stof

src/Input/TranslateTextRequest.php

@@ -82,8 +82,7 @@ final class TranslateTextRequest extends Input
      *   SourceLanguageCode?: string,
      *   TargetLanguageCode?: string,
      *   Settings?: TranslationSettings|array,
-     *
-     *   @region?: string,
+     *   '@region'?: string|null,
      * } $input
      */
     public function __construct(array $input = [])

src/TranslateClient.php

@@ -36,8 +36,7 @@ class TranslateClient extends AbstractApi
      *   SourceLanguageCode: string,
      *   TargetLanguageCode: string,
      *   Settings?: TranslationSettings|array,
-     *
-     *   @region?: string,
+     *   '@region'?: string|null,
      * }|TranslateTextRequest $input
      *
      * @throws InvalidRequestException