LibDebug: Add AttributeForm field to Dwarf::AttributeValue

In some contexts, it's helpful to also know the "Attribute Form",
in addition to the "Attribute Type".

An example for such context is the interpretation of the
"DW_AT_high_pc" attribute, which has different meaning if the form
is an address or a constant.

Userland/Libraries/LibDebug/Dwarf/AttributeValue.h

@@ -7,6 +7,7 @@
 #pragma once
 
 #include <AK/Types.h>
+#include <LibDebug/Dwarf/DwarfTypes.h>
 
 namespace Debug::Dwarf {
 
@@ -34,6 +35,8 @@ struct AttributeValue {
             const u8* bytes; // points to bytes in the memory mapped elf image
         } as_raw_bytes;
     } data {};
+
+    AttributeDataForm form {};
 };
 
 }