refactor: Hoist the pseudo-account field filter out of the auth check

The filter is constant, but building it inline meant a fresh std::set on
every IOU authorization check that reached the unauthorized-line branch,
including the ones on the trading paths. Build it once instead.

It is a function-local static rather than a namespace-scope one because the
SFields it points at are defined in another translation unit.

src/libxrpl/ledger/helpers/RippleStateHelpers.cpp

@@ -593,8 +593,12 @@ requireAuth(ReadView const& view, Issue const& issue, AccountID const& account,
             // can never authorize its own line and no transaction offers the
             // issuer a chance to do it either. Treat a line it already owns as
             // authorized, the same way MPT does.
+            //
+            // Function-local rather than namespace scope: the SFields it points
+            // at live in another translation unit.
+            static std::set<SField const*> const kPseudoAccountFilter{&sfVaultID, &sfLoanBrokerID};
             if (view.rules().enabled(fixCleanup3_4_0) &&
-                isPseudoAccount(view, account, {&sfVaultID, &sfLoanBrokerID}))
+                isPseudoAccount(view, account, kPseudoAccountFilter))
                 return tesSUCCESS;
 
             return TER{tecNO_AUTH};