Rename the layout decorator in case of conflict

[ssutar]

We used to rename the imported variable in case layout decorator has naming conflict.

There were 2 issues with the previous approach:

1. All occurrences of the variable need to be renamed in the current file, its hard to determine the local/global scoped var

2. It was not able to handle the cases where the layout is passed down to the child components. Not sure if this is standard pattern but I've seen few examples of it.

Its better to rename the decorator itself so that we don't have to update the local vars which might introduce unexpected behavior

So instead of transforming to

import { layout } from "@ember-decorators/component";
import templateLayout from "components/templates/foo";

@layout(templateLayout)
class Foo extends EmberObject {}

it should be:

import { layout as templateLayout } from "@ember-decorators/component";
import layout from "components/templates/foo";

@templateLayout(layout)
class Foo extends EmberObject {}