Migrate TestDox output to Event System

[sebastianbergmann]

When the --testdox CLI option is used in PHPUnit 9.5 then TestDox output replaces both the default progress output and the default result output.

When tests are reordered, then PHPUnit 9.5's TestDox printer redraws console output as needed to ensure consistent ordering of test results. @localheinz, @theseer, and I do not believe that the complexity added to the code by this is worth the benefit they provide.

With PHPUnit 10, the test result printer controlled by the --testdox CLI option will not emit any output before test execution has ended. Therefore redraw operations are no longer necessary.

While the tests are executed, the default progress information will be printed. This can be suppressed by using the new --no-progress CLI option.

This means that the --testdox CLI option in PHPUnit 10 only replaces the default test result output, not the default progress output.