Don't return binary file changes in raw PR diffs by default (#17158)

* return diffs without binary file content change

* ?binary=true option to restore old behaviour

Co-authored-by: techknowlogick <techknowlogick@gitea.io>
Co-authored-by: zeripath <art27@cantab.net>

templates/swagger/v1_json.tmpl

@@ -7400,6 +7400,12 @@
             "name": "diffType",
             "in": "path",
             "required": true
+          },
+          {
+            "type": "boolean",
+            "description": "whether to include binary file changes. if true, the diff is applicable with `git apply`",
+            "name": "binary",
+            "in": "query"
           }
         ],
         "responses": {