Support PHPUnit 12 by avoiding removed methods getMockForAbstractClass() and addMethods()

[crocodele]

This is an attempt to address #71 and support PHPUnit 12 by removing the use of the PHPUnit methods getMockForAbstractClass() and addMethods() that were deprecated in PHPUnit 11 and removed without replacements in PHPUnit 12.

It relies on a change in php-mock-integration, making the mock class non-abstract and adding an actual function that can be mocked using onlyMethods(). See https://github.com/php-mock/php-mock-integration/compare/master...crocodele:feature/SupportPhpUnit12?expand=1.

I haven't looked into the effects on php-mock-mockery and php-mock-prophecy, but can return to that if the general approach seems OK.

[rvalitov]

I guess the composer.json should also be changed to support PHPUnit 12 #76

[crocodele]

Needs the changes in php-mock/php-mock-integration#13 for the tests.

[crocodele]

OK, now the tests are finally passing. 🙂 I'll check Mockery and Prophecy next, to (hopefully) enable a stable release of php-mock/php-mock-integration.

[crocodele]

@michalbundyra, the tests in php-mock/php-mock-mockery and php-mock/php-mock-prophecy pass using php-mock/php-mock-integration 2.5.0-beta1, without any code changes. So it looks like the changes in 2.5.0-beta1 are breaking only for php-mock/php-mock-phpunit.

If this is enough in terms of testing, I think the remaining steps would be:

1. Release php-mock/php-mock-integration 3.0.0.
2. Bump the php-mock/php-mock-integration dependency to ^3.0.0 in this PR.
3. Create PRs in php-mock/php-mock-mockery and php-mock/php-mock-prophecy to widen the php-mock/php-mock-integration dependency to ^2.2.1 || ^3.0.0.
4. Review PRs, iterate if needed, merge the PRs and release new versions. 🙂

[michalbundyra]

@crocodele huge thanks 🙇