fix: #3587982 Modernize unit tests for PHPUnit 12 compatibility

Kim Pepperrequested to merge
issue/purge-3587982:3587982-modernize-phpunit into 8.x-3.x
  • Modernizes unit tests for PHPUnit 12 compatibility by replacing deprecated patterns:
    • Convert @dataProvider annotations to #[DataProvider] attributes with public static methods
    • Replace returnValue()/returnValueMap() with willReturn()/willReturnMap()
    • Replace getMockForTrait() with anonymous class using the trait
    • Remove deprecated @covers annotations
    • Convert @group annotations to #[Group] attributes

Closes #3587982

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