Add temporary listeners

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Add temporary listeners

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I wonder though if this can't just be implemented by the user like it is now. If it's a common/recurrent pattern we can think of some messenger-compatible helpers. Example:

export const registrationEvents = new SimpleEvent();
registerMethods({
	REGISTRATION: registrationEvents.emit
});

openTab('page.html');
const target = await registrationEvents.expectOne();

Previous attempt at this: pixiebrix/pixiebrix-extension@17e3d06 (#2237)

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Another example of a one-off listener:

https://github.com/pixiebrix/pixiebrix-extension/blob/12da1d02d23a4f4c209854c61a26522b904fac5d/src/background/util.ts#L70:L78