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/complete_includes.cpp

@@ -0,0 +1,5 @@
+#include "sample_heade
+#include <sys/cdef
+
+void foo() {}
+

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

@@ -0,0 +1,4 @@
+int main(int argc, char** argv)
+{
+    ar
+}

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

@@ -0,0 +1,5 @@
+int main(int argc, char** argv)
+{
+    int myvar1 = 3;
+    myv
+}

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

@@ -0,0 +1,7 @@
+struct MyStruct {
+    int x;
+};
+void foo()
+{
+    MyS
+}

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

@@ -0,0 +1,4 @@
+int main(int argc, char** argv)
+{
+    argv = nullptr;
+}

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(
+}

Userland/Libraries/LibCodeComprehension/Cpp/Tests/sample_header.h

@@ -0,0 +1,3 @@
+#pragma once
+
+int bar();