Expose name and alias in LookAheadMethods

[soerenmeier]

Currently it is only possible to get the name or if an alias is present the alias, or I'm missing something.
This exposed the name and alias separately. I'm not sure about the name field_unique_name.

[tyranron]

@soerenmeier I did some investigation on the naming and didn't find any consistency regarding the naming.

graphql-parse-resolve-info npm package has it in the following way:

• name: the name of the GraphQL field
• alias: the alias this GraphQL field has been requested as, or if no alias was specified then the name

graphql-ruby has only this:

#name ⇒ String(also: #graphql_name) readonly
The GraphQL name for this field, camelized unless camelize: false is provided.

#original_name ⇒ Symbol readonly
The original name of the field, passed in by the user.

So, I propose to remain field_unique_name as field_name, while the proposed field_name being named as field_original_name. This way, we'll preserve backwards compatibility and naming consistency over all the methods.