Support yoast/phpunit-polyfills v2

[swissspidy]

Not sure if we'll have problems in other packages with renaming test files...

Fixes #205

[thelovekesh]

LGTM!

[ernilambar]

I tested this PR is i18n command and got following output. Tests are running good but there are some deprecations. Not sure this is related to this PR or not. Pasting here for the info.

PHPUnit 10.5.20 by Sebastian Bergmann and contributors.

Runtime:       PHP 8.2.18
Configuration: /Users/nilambarsharma/Code/kli/i18n-command/phpunit.xml.dist

DDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDD..........                   47 / 47 (100%)

Time: 00:00.156, Memory: 10.00 MB

There was 1 PHPUnit test runner deprecation:

1) Your XML configuration validates against a deprecated schema. Migrate your XML configuration using "--migrate-configuration"!

--

2 tests triggered 2 PHPUnit deprecations:

1) WP_CLI\I18n\Tests\IterableCodeExtractorTest::test_gets_file_extension_correctly
Data Provider method WP_CLI\I18n\Tests\IterableCodeExtractorTest::file_extension_extract_provider() is not static

/Users/nilambarsharma/Code/kli/i18n-command/tests/IterableCodeExtractorTest.php:229

2) WP_CLI\I18n\Tests\IterableCodeExtractorTest::test_matches_file_extensions_correctly
Data Provider method WP_CLI\I18n\Tests\IterableCodeExtractorTest::file_extensions_matches_provider() is not static

/Users/nilambarsharma/Code/kli/i18n-command/tests/IterableCodeExtractorTest.php:244

OK, but there were issues!
Tests: 47, Assertions: 60, Deprecations: 33.

[swissspidy]

Thanks!
Yeah those deprecations need to be fixed in that command. They are triggered when using newer PHPUnit versions, which this PR enables.