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/rpc/mempool.cpp

@@ -25,7 +25,6 @@ using kernel::DumpMempool;
 
 using node::DEFAULT_MAX_RAW_TX_FEE_RATE;
 using node::MempoolPath;
-using node::ShouldPersistMempool;
 using node::NodeContext;
 
 static RPCHelpMan sendrawtransaction()

src/rpc/output_script.cpp

@@ -26,11 +26,6 @@
 #include <tuple>
 #include <vector>
 
-namespace node {
-struct NodeContext;
-}
-using node::NodeContext;
-
 static RPCHelpMan validateaddress()
 {
     return RPCHelpMan{

src/rpc/rawtransaction.cpp

@@ -46,12 +46,10 @@
 #include <univalue.h>
 
 using node::AnalyzePSBT;
-using node::BroadcastTransaction;
 using node::FindCoins;
 using node::GetTransaction;
 using node::NodeContext;
 using node::PSBTAnalysis;
-using node::ReadBlockFromDisk;
 
 static void TxToJSON(const CTransaction& tx, const uint256 hashBlock, UniValue& entry, CChainState& active_chainstate)
 {