LR: Attribute access with non local declaration should share the same declaration when possible

[jecisc]

Imagine this piece of code:

import x

a(x.y)
b(x.y)

In this case we will have a declaration of x in the import and 3 usage (import, first usage and second usage).

For y, we will create a FASTNonLocalDeclaration since we do not have its declaration locally. But currently we will create one for the first attribute access and one for the second attribute access.

In the future since they are accessed identically and nothing got redefined in between they should share the same FASTNonLocalDeclaration.