[Yaml] Fixed the escaping of strings starting with a dash when dumping

Dashes need to be escaped in character sets in regexes as they are used to
specify a range otherwise.
Refs #9039
Merge branch '2.2' into 2.3

* 2.2:
  [DoctrineBridge] Loosened CollectionToArrayTransformer::transform() to accept arrays
  Removed unused use statements.
  Make usleep longer and simplify assertions
  Added japanese translation resource for security component.
  [Yaml] Fixed the escaping of strings starting with a dash when dumping
  Fix in ChainLoader.php
  fixed wrong started states
Merge branch '2.3'

* 2.3:
  Improve documentation of X-Forwarded-For header handling
  [DoctrineBridge] Loosened CollectionToArrayTransformer::transform() to accept arrays
  Removed unused use statements.
  Make usleep longer and simplify assertions
  Added japanese translation resource for security component.
  Replaced the @inheritdoc with an actual list of params since the original method has a different signature.
  fix typo : StdClass should be stdClass with little "s"
  Remove unnecessary continue from Request
  [Yaml] Fixed the escaping of strings starting with a dash when dumping
  Fix in ChainLoader.php
  fixed wrong started states