Use placeholders for local function names in function calls

[angelikatyborska]

Input

defmodule HelloWorld do
  def hello(name) do
    "Hello, #{name}"
  end

  def hello() do
    hello("Alice")
  end
end

Desired output

A local function, when called, is referenced by the same placeholder name as when defined.

defmodule(PLACEHOLDER_1) do
  def(PLACEHOLDER_2(PLACEHOLDER_3)) do
    "Hello, #{PLACEHOLDER_3}"
  end
  def(PLACEHOLDER_2()) do
    PLACEHOLDER_2("Alice")
  end
end

Current output

Function names in function calls are not replaced by placeholders.

defmodule(PLACEHOLDER_1) do
  def(PLACEHOLDER_2(PLACEHOLDER_3)) do
    "Hello, #{PLACEHOLDER_3}"
  end
  def(PLACEHOLDER_2()) do
    hello("Alice")
  end
end

Please add extensive tests for various scenarios.