HEAD broken on - updates required for prophecy 1.10.0

Problem/Motivation

Something in phpspec/prophecy 1.10.0 makes our tests fail on php7.3

They were passing previously

See https://github.com/phpspec/prophecy/compare/1.9.0...1.10.0
And https://github.com/phpspec/prophecy/pull/446

https://github.com/phpspec/prophecy/pull/446 changed the way that comparison for the default token (ExactValueToken) is done for closures.

With prophecy, when you do this:

$this->prophesize(Some:class)->someMethod($some_argument);

Internally it turns $some_argument into new \Prophecy\Argument\Token\ExactValueToken($some_argument) and then calls \Prophecy\Argument\Token\ExactValueToken::scoreArgument which now returns false if the comparator throws a ComparisonFailure

For closures, the comparator used is \Prophecy\Comparator\ClosureComparator which always throws a ComparisonFailure

Proposed resolution

The fix, is to use the long-form and instead of using the default ExactValueToken, use Argument::is() which maps to \Prophecy\Argument\Token\IdenticalValueToken which just does a straight equality comparison, which is fine for the two closures in the test that are broken.

The code we're calling in core that is failing

$this->decoratedFormState->prepareCallback($unprepared_callback)
      ->willReturn($prepared_callback)
      ->shouldBeCalled();

    $this->assertSame($prepared_callback, $this->formStateDecoratorBase->prepareCallback($unprepared_callback));

Where in this scenario, $unprepared_callback and $prepared_callback is a closure, causing the fail.

We actually expect direct equality here, so we should use Argument::is

Remaining tasks

User interface changes

API changes

Data model changes

Release notes snippet