Fix missing proxy problem in lambda lift.

Binding of free variables is deferred to delambdafy phase.
However, bodies of lambdas might call to methods that get
transformed in lambdalift phase and that introduces new
free variables to lambdas. Therefore, we have to transform
bodies of lambdas and supply additional arguments to methods
being transformed by lambdalift but we should skip proxy lookup.
Again, the proxy lookup should be skipped because free variables
of lambdas itself are addressed in delambdafy phase.

This change introduced proper logic for skipping proxies.

Added a test-case which demonstrates problematic scenario.

TODO: test more involved scenarios where lambda bodies are nested in
local methods to see if all possible permutations of nesting structure
are handled properly.