run-tests.sh - move suite determination from WorkAllocator to PhpUnitTestDiscovery

Problem/Motivation

This code in WorkAllocator

  private function getTestTypeWeight(string $class): int {
    assert(class_exists($class), "$class does not exist");
    return match(TRUE) {
      is_subclass_of($class, WebDriverTestBase::class) => 3,
      is_subclass_of($class, BrowserTestBase::class) => 2,
      is_subclass_of($class, BuildTestBase::class) => 2,
      is_subclass_of($class, KernelTestBase::class) => 1,
      default => 0,
    };
  }

makes it hard to unit test it with fixtures, because fixture is dependent on the existence of the test class.

Proposed resolution

Rely on the determination done in PhpUnitTestDiscovery instead of checking existence and inheritance in WorkAllocator.

Remaining tasks

User interface changes

Introduced terminology

API changes

Data model changes

Release notes snippet