script: Let canvas serialization to image fail gracefully (#37184)

Instead of panicking when serialization of canvas to image data (whether
through `toBlob()` or via `toDataURL()`), properly handle failed
serialization. This is an implementation of the appropriate error
handling from the specification text.

Testing: This change includes a new Serov-specific test, because it is
impossible to know what the canvas size limits are of all browsers.
Fixes: #36840.

Signed-off-by: Martin Robinson <mrobinson@igalia.com>

tests/wpt/mozilla/meta/MANIFEST.json

@@ -12850,6 +12850,13 @@
       ]
      ]
     },
+    "canvas-oversize-serialization.html": [
+     "3330ee2b8c4e33a18a3e17151fd7c398c9a5d024",
+     [
+      null,
+      {}
+     ]
+    ],
     "canvas.initial.reset.2dstate.html": [
      "e276ed09ffcf16eff16b784c622b93665c4109ee",
      [