Reduce redundancy in the RequestGraph's file nodes

[gorakong]

↪️ Pull Request

This PR reduces redundancy in the RequestGraph's file nodes (which account for close to 50% of the RequestGraph's nodes) by getting rid of the value object in each of them, since these can be derived from their IDs. On a large app, this nets us a 6.3% reduction in the size of the serialized RequestGraph.

💻 Examples

Before:

  {
    id: 'node_modules/glob-parent/index.js',
    type: 'file',
    value: { filePath: 'node_modules/glob-parent/index.js' }
  }

After:

{ id: 'node_modules/glob-parent/index.js', type: 'file' }