LibCodeComprehension: Re-organize code comprehension related code

This moves all code comprehension-related code to a new library,
LibCodeComprehension.

This also moves some types related to code comprehension tasks (such as
autocomplete, find declaration) out of LibGUI and into
LibCodeComprehension.

Userland/Libraries/LibCodeComprehension/Cpp/Tests/parameters_hint1.cpp

@@ -0,0 +1,8 @@
+void foo(int x, char y);
+
+void bar()
+{
+    foo();
+    foo(123, 'b');
+    foo(
+}