Merge bitcoin/bitcoin#25466: ci: add unused-using-decls to clang-tidy

a02f3f19f5 tidy: use misc-unused-using-decls (fanquake)
d6787bc19b refactor: remove unused using directives (fanquake)
3617634324 validation: remove unused using directives (eugene)

Pull request description:

  Adds https://clang.llvm.org/extra/clang-tidy/checks/misc/unused-using-decls.html to our clang-tidy.
  PR'd after the discussion in #25433 (which it includes).

ACKs for top commit:
  jamesob:
    Github ACK a02f3f19f5

Tree-SHA512: 2bb937c1cc90006e69054458d845fb54f287567f4309c773a3fc859f260558c32ff51fc1c2ce9b43207426f3547e7ce226c87186103d741d5efcca19cd355253

src/test/coinstatsindex_tests.cpp

@@ -13,9 +13,6 @@
 
 #include <chrono>
 
-using kernel::CCoinsStats;
-using kernel::CoinStatsHashType;
-
 BOOST_AUTO_TEST_SUITE(coinstatsindex_tests)
 
 static void IndexWaitSynced(BaseIndex& index)

src/test/miniscript_tests.cpp

@@ -120,6 +120,8 @@ struct KeyConverter {
 //! Singleton instance of KeyConverter.
 const KeyConverter CONVERTER{};
 
+// https://github.com/llvm/llvm-project/issues/53444
+// NOLINTNEXTLINE(misc-unused-using-decls)
 using miniscript::operator"" _mst;
 
 enum TestMode : int {