Fix PHP 8.1 incompatibility errors

[szeber]

In PHP 8.1 a new deprecation error is triggered because the getIterator() and getCount() methods don't conform to the built in Traversable and Countable interfaces.

For example: PHP Deprecated: Return type of WMDE\PsrLogTestDoubles\LogCalls::getIterator() should either be compatible with IteratorAggregate::getIterator(): Traversable, or the #[\ReturnTypeWillChange] attribute should be used to temporarily suppress the notice and PHP Deprecated: Return type of WMDE\PsrLogTestDoubles\LogCalls::count() should either be compatible with Countable::count(): int, or the #[\ReturnTypeWillChange] attribute should be used to temporarily suppress the notice

The 2 ways to fix this is either add an attribute is either to add the return typehint or to add the attribute. Since on PHP 7.1 these methods didn't have a return typehint, and covariance/contravariance is only fully supported in 7.4, adding the attribute should be more backwards compatible because they will just be treated as comments versions before 8.0.

[JeroenDeDauw]

Thank you @szeber! I have added the return types. Temporarily in a different repo and composer package: https://github.com/JeroenDeDauw/PsrLogTestDoubles. Or perhaps not. Depends on if WMDE is willing to move over this repo. Either way I will continue maintaining the new version.

[gbirke]

We now have a new 3.2 release that's 8.x compatible and will continue to support this repo