fix: aliased internal modules that look like core modules

[echenley]

What

Update isBuiltIn to return false if a path is returned from a resolver.
Previously an alias like 'constants/foo' would be classified as a builtin rather than internal since 'constants' is a core module of node. Fixes one of the issues mentioned in #1034.

Update webpack resolver to attempt to resolve modules internally before classifying them as builtin.

Add several tests to cover these cases.

Example

project
└── src
    └── constants
        └── index.js

{
  "settings": {
    "import/resolver": {
      "node": {
        "paths": ["/project/src"]
      }
    }
  }
}

Result:

// BEFORE
import { FOO } from 'constants/index'
import { isObject } from 'lodash'

// AFTER
import { isObject } from 'lodash'
import { FOO } from 'constants/index'

[coveralls]

Coverage increased (+0.001%) to 97.863% when pulling ba0aed9 on echenley:ech/fix-isBuiltIn-local-aliases into 0ff1c83 on benmosher:master.

[karuana]

When will this PR be merged?
I am waiting for this PR to be merged. 😭😭😭