Issue #2216551 by jhodgdon: Fill in topic/@defgroup docs for Services/DIC.
Issue #2313089 by er.pushpinderrana, undertext | jhodgdon: Fixed Form generation topic needs quick follow-up fix.
Issue #2313627 by er.pushpinderrana | jhodgdon: Fixed FormStateInterface needs @ingroup.
Issue #2304461 by sun: Rebase KernelTestBase onto PHPUnit.

Includes various performance optimizations, since ContainerBuilder::compile()
is very slow: A precompiled Container is shared across test methods.
Each test boots new DrupalKernel that gets the precompiled Container
injected.

Each test registers itself as a Logger, so as to catch unexpected error
log messages, in case functional code fails to use trigger_error().

Various utility methods of the former Simpletest TestBase + KernelTestBase
are made available as traits (so as to keep the original code functional).
Issue #2304461 by sun: Fixed DependencySerializationTrait breaks sans container.
[interim] PHPUnit process isolation fixes.

- Fix process isolation infinitely blocks on Windows.
  https://github.com/sebastianbergmann/phpunit/pull/1340
- Fix standard IO streams are not defined in process isolation.
  https://github.com/sebastianbergmann/phpunit/pull/1348
- Fix isolated child process leaks into parent process.
  https://github.com/sebastianbergmann/phpunit/issues/1351
[temp] Re-route former KTB to new KTB.
Issue #2306539 by sun: Fixed FieldUnitTestBase::createFieldWithInstance() pollutes test class with arbitrary properties.
Issue #2314123 by sun: Fixed lots of bogus tests.
Updated File API tests for properly compiled DrupalKernel.
Updated Database tests for new KernelTestBase environment.
Updated ModuleHandlerTest for new KernelTestBase environment.
Fixed (bogus) error reporting in ViewExecutable for new KernelTestBase.
[FIXME] system_cron() hard-codes database queries on 'queue'.
[FIXME] ConfigImporter hides errors.
[FIXME] PhpStorageFactory does not support stream wrappers.
[FIXME] drupal_rewrite_settings() does not support stream wrappers.
[FIXME] Config\FileStorage does not support stream wrappers.
Issue #2313989 by sun: Update vfsStream to 1.3.0.
Issue #2301245 by sun: Fixed Entity system invokes non-existing theme hooks: "Theme hook $entity_type_id not found.".