swagger validate should flag GET operations with body parameters as errors

Running swagger validate against a spec that includes GET operations with parameters in the body does not produce any errors or warnings for any version of OpenAPI.

HTTP GET requests that have a body were only very recently added to the HTTP spec itself and are not allowed by OpenAPI prior to version 3.1. In the first place, specs which claim to be using the older version which contain these types of operations are not valid. In the second place even for users of OpenAPI 3.1, there are very good reasons to want to forbid these sorts of operations depending on what external HTTP clients are going to be accessing the API. So ideally I would want some option for swagger validate to enforce this as a standard even when validating a 3.1 spec.

The absence of this validation causes user confusion because the specs in question are also not generally compatible with most browsers, so people are opening issues like this one: #4327

Start at the swagger validate entry point and trace how request bodies and OpenAPI versions are validated, using the behavior described in #4327 as context. Done means GET operations with body parameters are rejected for OpenAPI versions before 3.1, with an option to enforce the restriction for 3.1 specifications.