ci: Run iwyu on all src files #27571

Mind elaborating about skipping walletutil?

because it crashes. See:

# python3 "/include-what-you-use/iwyu_tool.py" -p . ./src/wallet/walletutil.cpp -j 9 -- -Xiwyu --cxx17ns -Xiwyu --mapping_file="$PWD/contrib/devtools/iwyu/bitcoin.core.imp"  
In file included from wallet/walletutil.cpp:5:
In file included from ./wallet/walletutil.h:8:
In file included from ./script/descriptor.h:8:
In file included from ./outputtype.h:9:
In file included from ./script/signingprovider.h:10:
In file included from ./key.h:10:
In file included from ./pubkey.h:10:
In file included from ./hash.h:10:
In file included from ./crypto/common.h:12:
In file included from /usr/lib64/clang/16/include/stdint.h:52:
In file included from /usr/include/stdint.h:26:
In file included from /usr/include/bits/libc-header-start.h:33:
/usr/include/features.h:413:4: warning: _FORTIFY_SOURCE requires compiling with optimization (-O) [-W#warnings]
#  warning _FORTIFY_SOURCE requires compiling with optimization (-O)
   ^
In file included from wallet/walletutil.cpp:5:
In file included from ./wallet/walletutil.h:8:
In file included from ./script/descriptor.h:8:
In file included from ./outputtype.h:9:
In file included from ./script/signingprovider.h:10:
In file included from ./key.h:10:
In file included from ./pubkey.h:10:
In file included from ./hash.h:14:
In file included from ./serialize.h:17:
In file included from /usr/lib/gcc/x86_64-redhat-linux/13/../../../../include/c++/13/memory:78:
/usr/lib/gcc/x86_64-redhat-linux/13/../../../../include/c++/13/bits/unique_ptr.h:97:16: error: invalid application of 'sizeof' to an incomplete type 'wallet::DescriptorScriptPubKeyMan'
        static_assert(sizeof(_Tp)>0,
                      ^~~~~~~~~~~
/usr/lib/gcc/x86_64-redhat-linux/13/../../../../include/c++/13/bits/unique_ptr.h:404:4: note: in instantiation of member function 'std::default_delete<wallet::DescriptorScriptPubKeyMan>::operator()' requested here
          get_deleter()(std::move(__ptr));
          ^
/usr/lib/gcc/x86_64-redhat-linux/13/../../../../include/c++/13/bits/stl_construct.h:151:19: note: in instantiation of member function 'std::unique_ptr<wallet::DescriptorScriptPubKeyMan>::~unique_ptr' requested here
      __pointer->~_Tp();
                  ^
/usr/lib/gcc/x86_64-redhat-linux/13/../../../../include/c++/13/bits/stl_construct.h:196:2: note: in instantiation of function template specialization 'std::_Destroy_aux<false>::__destroy<std::unique_ptr<wallet::DescriptorScriptPubKeyMan> *>' requested here
        __destroy(__first, __last);
        ^
/usr/lib/gcc/x86_64-redhat-linux/13/../../../../include/c++/13/bits/alloc_traits.h:947:7: note: in instantiation of function template specialization 'std::_Destroy<std::unique_ptr<wallet::DescriptorScriptPubKeyMan> *>' requested here
      _Destroy(__first, __last);
      ^
/usr/lib/gcc/x86_64-redhat-linux/13/../../../../include/c++/13/bits/stl_vector.h:732:7: note: in instantiation of function template specialization 'std::_Destroy<std::unique_ptr<wallet::DescriptorScriptPubKeyMan> *, std::unique_ptr<wallet::DescriptorScriptPubKeyMan>>' requested here
        std::_Destroy(this->_M_impl._M_start, this->_M_impl._M_finish,
             ^
./wallet/walletutil.h:122:8: note: in instantiation of member function 'std::vector<std::unique_ptr<wallet::DescriptorScriptPubKeyMan>>::~vector' requested here
struct MigrationData
       ^
./wallet/walletutil.h:119:7: note: forward declaration of 'wallet::DescriptorScriptPubKeyMan'
class DescriptorScriptPubKeyMan;
      ^