Change the way schemas are exported

[smoya]

Part of asyncapi/parser-js#481

This change, once ported to next-major branch, will make https://github.com/asyncapi/parser-js/blob/next-major/src/schema-parser/asyncapi-schema-parser.ts#L38-L53 to provide wrong types.

TBH is not an issue with this PR per se. The way we are exporting the schemas is not helping. I think we could introduce the following separation in next-major branch:

declare const _exports: {
    'schemas': {
        // ...
    },
    'schemas-without-$id': {
        // ...
    }
}

Do you think it makes sense? If it does, +1 to merge this and start doing those changes in next-major.

cc @magicmatatjahu @jonaslagoni

Originally posted by @smoya in #298 (comment)