iwyu: Add temporary mapping to work around upstream bug

contrib/devtools/iwyu/bitcoin.core.imp

@@ -5,4 +5,8 @@
   { "include": [ "<mmintrin.h>", "private", "<immintrin.h>", "public" ] },
   { "include": [ "<smmintrin.h>", "private", "<immintrin.h>", "public" ] },
   { "include": [ "<tmmintrin.h>", "private", "<immintrin.h>", "public" ] },
+
+  # Workaround for IWYU issue.
+  # See: https://github.com/include-what-you-use/include-what-you-use/issues/2084.
+  { "symbol": ["std::tuple", "private", "<tuple>", "public"] },
 ]

src/script/signingprovider.cpp

@@ -13,6 +13,7 @@
 
 #include <algorithm>
 #include <cstddef>
+#include <variant>
 
 const SigningProvider& DUMMY_SIGNING_PROVIDER = SigningProvider();
 

src/script/signingprovider.h

@@ -25,7 +25,6 @@
 #include <span>
 #include <tuple>
 #include <utility>
-#include <variant>
 #include <vector>
 
 class MuSig2SecNonce;