[CodeQuality] Assert compare on countable

[peterfox]

Changes

• Adds the new rule AssertCompareOnCountableWithMethodToAssertCountRector
• Adds a test
• Updates the docs

Why

Based on this PHPStan PHPUnit rule it will convert comparison on Countable objects with the count method to use the assertCount method instead.

Works with method and static method calls.

-$this->assertSame(1, $countable->count());
+$this->assertCount(1, $countable);

[TomasVotruba]

Thank you 😊