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/CodeComprehensionEngine.cpp

@@ -0,0 +1,42 @@
+/*
+ * Copyright (c) 2021, Itamar S. <itamar8910@gmail.com>
+ * Copyright (c) 2022, the SerenityOS developers.
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include "CodeComprehensionEngine.h"
+
+namespace CodeComprehension {
+
+CodeComprehensionEngine::CodeComprehensionEngine(FileDB const& filedb, bool should_store_all_declarations)
+    : m_filedb(filedb)
+    , m_store_all_declarations(should_store_all_declarations)
+{
+}
+
+void CodeComprehensionEngine::set_declarations_of_document(String const& filename, Vector<Declaration>&& declarations)
+{
+    // Callback may not be configured if we're running tests
+    if (!set_declarations_of_document_callback)
+        return;
+
+    // Optimization - Only notify callback if declarations have changed
+    if (auto previous_declarations = m_all_declarations.find(filename); previous_declarations != m_all_declarations.end()) {
+        if (previous_declarations->value == declarations)
+            return;
+    }
+    if (m_store_all_declarations)
+        m_all_declarations.set(filename, declarations);
+    set_declarations_of_document_callback(filename, move(declarations));
+}
+
+void CodeComprehensionEngine::set_todo_entries_of_document(String const& filename, Vector<TodoEntry>&& todo_entries)
+{
+    // Callback may not be configured if we're running tests
+    if (!set_todo_entries_of_document_callback)
+        return;
+    set_todo_entries_of_document_callback(filename, move(todo_entries));
+}
+
+}