[core] optimize #include directives in core cpp files (#10717)

This commit removes unnecessary `#include` directives in core `cpp`
files that already include `instance.hpp`. The `instance.hpp` header
itself includes all necessary OT core headers and definitions as they
are contained within an `ot::Instance`.

src/core/thread/dua_manager.cpp

@@ -35,17 +35,7 @@
 
 #if OPENTHREAD_CONFIG_DUA_ENABLE || (OPENTHREAD_FTD && OPENTHREAD_CONFIG_TMF_PROXY_DUA_ENABLE)
 
-#include "common/as_core_type.hpp"
-#include "common/code_utils.hpp"
-#include "common/log.hpp"
-#include "common/settings.hpp"
 #include "instance/instance.hpp"
-#include "net/ip6_address.hpp"
-#include "thread/mle_types.hpp"
-#include "thread/thread_netif.hpp"
-#include "thread/thread_tlvs.hpp"
-#include "thread/uri_paths.hpp"
-#include "utils/slaac_address.hpp"
 
 namespace ot {