Add retry callback

[fregante]

For situations like https://github.com/pixiebrix/pixiebrix-source/pull/1438

It would replace:

const offscreenPage = { page: "offscreen" };

export const clearRecordings = wrapEnsureOffscreenDocumentInBackground(
  getMethod("CLEAR_RECORDINGS", offscreenPage),
);

with

const offscreenPage = { page: "offscreen", retryCallback: ensureOffscreenDocument };

export const clearRecordings = getMethod("CLEAR_RECORDINGS", offscreenPage);

which will call ensureOffscreenDocument after the first failure. The callback will be called with the error received so it can determine whether it's related to a missing offscreen (however it the internal retry logic I think only fails in case of broken communication)