Provide a convenience API for testing error constructor and message

[gajus]

Description

The current API:

.throws(function|promise, [error, [message]])

only allows to define constructor of the error and requires to test message separately, e.g.

const error = await t.throws(createReservation(undefined, parameters, context), UserError);

t.true(error.message === 'Ticket selection cannot be empty.');

By the way, .throws(function|promise, [error, [message]]) is slightly misleading.
At first I thought the third parameter is the error message, i.e.
t.throws(createReservation(undefined, parameters, context), 'Ticket selection cannot be empty.');.

It would be convenient to be able to construct the error as such:

await t.throws(createReservation(undefined, parameters, context), new UserError(Ticket selection cannot be empty.));

In such case, ava would need to check that the constructor of the object and the message match.

[sindresorhus]

Duplicate of #1047. I agree it's currently sub-optimal. You should be able to assert the different specifics of an error in one assertion. See my proposal #1047 (comment) and add your thoughts there.