Release 7.5.0

• Code generation of endpoint classes using the API specification of Elasticsearch 7.5.0
  commit ec0e0aa
• Fixed Client::extractArgument iterable casting to array; this allows passing a Traversable body for some endpoints (e.g. Bulk, Msearch, MsearchTemplate)
  #983
• Fixed the Response Exception if the reason field is null
  #980
• Added support for PHP 7.4
  #976