Kernel: Fix and cleanup a lot of AML code

Node now have APIs to convert them to buffer, integer and string. This
allows possibility to handle methods that need explicitly use one of the
overloads instead of integer.

This patch also adds handling of DebugOp. This is used quite heavily in
uACPIs test suite.

kernel/CMakeLists.txt

@@ -7,7 +7,9 @@ set(KERNEL_SOURCES
 	kernel/ACPI/AML/Namespace.cpp
 	kernel/ACPI/AML/Node.cpp
 	kernel/ACPI/AML/Package.cpp
+	kernel/ACPI/AML/Register.cpp
 	kernel/ACPI/AML/Scope.cpp
+	kernel/ACPI/AML/String.cpp
 	kernel/APIC.cpp
 	kernel/BootInfo.cpp
 	kernel/CPUID.cpp