fix: internal root level reference do not resolve

[jonaslagoni]

This PR addresses the issue where root level references to internal schema definitions are not resolved accurately.

Fixes https://github.com/APIDevTools/json-schema-ref-parser/issues/201

[jonaslagoni]

So, I am not quite sure of the best cause of action to solve this issue, so might need some pointers from someone who knows the code more in-depth 😄

Trying to dereference the input in the tests the following happens:

1. First pass, the reference is being dereferenced - https://github.com/APIDevTools/json-schema-ref-parser/blob/f6886ab9ee576754791f2a194b140a637dd98a87/lib/dereference.js#L50
2. Then the pointer is resolved, it says it is a circular reference (and I cant figure out whether that is incorrect behavior) and the resolved value is the root schema when I believe it should be the resolved definition schema name. - https://github.com/APIDevTools/json-schema-ref-parser/blob/f6886ab9ee576754791f2a194b140a637dd98a87/lib/dereference.js#L133

   pointer = {
   ...,
   path: "/Users/lagoni/Documents/AsyncAPI/json-schema-ref-parser/test/specs/root-internal/root-internal.yaml#/definitions/name",
   originalPath: "/Users/lagoni/Documents/AsyncAPI/json-schema-ref-parser/test/specs/root-internal/root-internal.yaml#/definitions/name",
   value: {
   definitions: {
     name: {
       title: "name",
       type: "object",
       required: [
         "first",
         "last",
       ],
       properties: {
         first: {
           type: "string",
         },
         last: {
           $ref: "#/definitions/name/properties/first",
         },
       },
     },
   },
   $ref: "#/definitions/name",
   },
   circular: true,
   indirections: 0,
   }

3. Since the pointer is marked as circular, this means that the rest of the references are not crawled, which then means the $ref within the definition is not iterated, which to me indicate that there are multiple places that need to change, but I might be wrong 😅 - https://github.com/APIDevTools/json-schema-ref-parser/blob/f6886ab9ee576754791f2a194b140a637dd98a87/lib/dereference.js#L151

But from this point on, I do not know where or what to try and poke at...

Any suggestions?

cc @philsturgeon (as you are the most recently pushed changed, feel free to re-tag someone else 😄)

[jonaslagoni]

With no interest, closing.