Add a forward-compatibility wrapper for phpunit8 assertions
Add a forward-compatibility wrapper for phpunit8 assertions

While doctrine still supports php7.2 the test cases need to run
under phpunit8 as well. However some assertion methods produce
deprecation warnings in the test output with phpunit >= 9.

This commit adds a thin forward compatiblity wrapper for the
new assertion method names so that they can be used with both
supported phpunit versions.

doctrine/doctrine2,doctrine/doctrine2,bigfoot90/doctrine2,bigfoot90/doctrine2