Merge branch '6.4' into 7.0

* 6.4:
  [FrameworkBundle][Validator] Replace annotation by attribute
  [Validator] Add annotation in Constraint
  [Lock] Add some missing return types in tests
  [Clock] Throw `DateMalformedStringException`/`DateInvalidTimeZoneException` when appropriate
  [VarExporter] Remove unused test files
  [FrameworkBundle] Remove unused test file
  [DependencyInjection] Remove unused test file
  [DomCrawler] Added argument `$default` to method `Crawler::attr()`
  [HttpKernel] Fix missing Request in RequestStack for StreamedResponse
  Psalm: Ignore UnusedClass errors
  fix(console): avoid multiple new line when message already ends with a new line

Author: nicolas-grekas