fix(Bug): Update Dgraph Alias to work with GQL aliases

[all-seeing-code]

Motivation

This PR fixes: GRAPHQL-1078 Before this fix following query used to append aliase'd predicate in lambda resolved field.

query {
  queryUser {
    id
    actualName: name
    name: email # email field has been aliased as name which is another field in this type and is used by lambda
    intro
  }
}

Components affected by this PR

GraphQL resolver

Does this PR break backwards compatibility?

No

Testing

Added following tests in:

1. e2e test with alias
2. Resolver test with alias

Fixes

Fixes GRAPHQL-1078

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This change is 

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