feat(openapi): reflect specification to OpenAPI 3.1

[LoicBoursin]

Q	A
Branch?	main
Tickets	#4069
License	MIT
Doc PR	N/A

[soyuka]

From @Chris53897

There are a lot of changes with 3.1.
https://github.com/OAI/OpenAPI-Specification/releases/tag/3.1.0-rc0

format (whether byte, binary, or base64) is no longer used to describe file payloads. As part of JSON Schema compliance, now contentEncoding and contentMediaType can be used for such specification.

Docs should be updated after merging. https://api-platform.com/docs/core/file-upload/#configuring-the-entity-receiving-the-uploaded-file

[LoicBoursin]

OpenAPI documents validation fails in test because OpenAPI 3.1 is not yet supported by swagger-parser. It will be fixed by APIDevTools/swagger-parser#171