Implement new simplified channel parameters

[smoya]

Apply the changes introduced by asyncapi/spec#935

Regarding the changes in Parser-JS, we don’t really need to do a lot because we can keep the current API -> schema(): Schema | undefined
However, things like parameter.schema().example() will now require to return the value from the parameter.example() which is basically the parent level.

In that way, we don’t need to add a breaking change in the parser-api. Internally, we can create a new object called simplifiedSchema or similar, that inherits the behaviour from the Schema object, but only “allowing” the enum, default, and examples methods, logging a warning message when using the others.

Remember that including any non-supported field in the parameter will make any ASyncAPI v3 document to become invalid, so it is not expected developers call any other method from the schema (but still, logging a warning message its a good idea)

[jonaslagoni]

Pretty sure this is done 😄