Prepare 6.0.0 beta release (OpenAPITools#12039)

* update to 6.0.0-beta

* update samples

Prepare 5.4.0 release (OpenAPITools#11457)

* prepare 5.4.0 release

* update gradle tests

Prepare 5.3.1 release (OpenAPITools#11161)

* prepare v5.3.1 release

* update samples

Prepare v5.3.0 release (OpenAPITools#10680)

* prepare 5.3.0 release

* remove docker-tag-latest-release

Prepare 5.2.1 release (OpenAPITools#10161)

* prepare for 5.2.1 release

* update samples

Prepare v5.2.0 release (OpenAPITools#9920)

* 5.2.0 release

* update samples

* update meta codegen

v5.1.1 release (OpenAPITools#9421)

Prepare v5.1.0 release (OpenAPITools#9017)

* prepare v5.1.0 release

* update samples (dart-dio-next)

Prepare v5.0.1 release (OpenAPITools#8627)

* release 5.0.1

* update samples

Prepare v5.0.0 release (OpenAPITools#8247)

* update to 5.0.0

* update samples