FIX Ensure constructors are populated in mocks of interfaces in PHP 8

[Cheddam]

See https://news-web.php.net/php.internals/109377

This is a legitimate issue caused by a change in PHP's behaviour, and was fixed upstream in PHPUnit 9, so it makes sense to implement the same patch here.

Fixes #7.

[sminnee]

Looks good but could involve less copy/pasta

[Cheddam]

Have added test coverage.

[sminnee]

For some reason this is failing with an undefined XDEBUG_CC_UNUSED constant being referenced on php 7.3, 7.4, and nightly

[Cheddam]

I've looked into the failures:

Xdebug 3 is now installed on builds running PHP 7.3 and later

Xdebug 3 completely revised the available configuration options, throwing warnings when any old settings are set or accessed. This requires a change in the way Xdebug is configured (using XDEBUG_MODE=coverage), but also changes to the phpunit/php-code-coverage package, which has checks against these old settings. A fix is present in the current release of this package, but as with the rest of PHPUnit we're stuck on an extremely old one, so forking may be required.

php-token-stream outdated

The (now deprecated) php-token-stream package does not have full PHP 8 support on the version we're using (currently 2.0.2 - 4.0.4 is required.) I've tested adding an explicit dependency on it with a remap (4.0.4 as 2.0.2), and this seems to work fine, except that 4.0.4 doesn't support PHP 7.2 and earlier (which is the main reason this package received new major releases.) We could drop older PHP builds to resolve this, or monkey patch the updated requirement into PHP 8 CI builds.

@sminnee Thoughts on how to proceed? We won't have any green builds on this repository (nor sminnee/phpunit) until this is resolved 😔

[Cheddam]

I'll close this for the time being - if down the road we decide to invest the unreasonable amount of effort required to get the builds green and continue maintaining this fork, the diff is here as a reference.