random: replace construct/assign with explicit Reseed()

src/test/orphanage_tests.cpp

@@ -106,7 +106,7 @@ BOOST_AUTO_TEST_CASE(DoS_mapOrphans)
     // ecdsa_signature_parse_der_lax are executed during this test.
     // Specifically branches that run only when an ECDSA
     // signature's R and S values have leading zeros.
-    g_insecure_rand_ctx = FastRandomContext{uint256{33}};
+    g_insecure_rand_ctx.Reseed(uint256{33});
 
     TxOrphanageTest orphanage;
     CKey key;