scripted-diff: [test] Use g_rng/m_rng directly

-BEGIN VERIFY SCRIPT-

 # Use m_rng in unit test files
 ren() { sed -i "s:\<$1\>:$2:g" $( git grep -l "$1" src/test/*.cpp src/wallet/test/*.cpp src/test/util/setup_common.cpp ) ; }
 ren InsecureRand32                m_rng.rand32
 ren InsecureRand256               m_rng.rand256
 ren InsecureRandBits              m_rng.randbits
 ren InsecureRandRange             m_rng.randrange
 ren InsecureRandBool              m_rng.randbool
 ren g_insecure_rand_ctx           m_rng
 ren g_insecure_rand_ctx_temp_path g_rng_temp_path

-END VERIFY SCRIPT-

src/test/validation_flush_tests.cpp

@@ -145,7 +145,7 @@ BOOST_AUTO_TEST_CASE(getcoinscachesizestate)
         chainstate.GetCoinsCacheSizeState(MAX_COINS_CACHE_BYTES, 0),
         CoinsCacheSizeState::CRITICAL);
 
-    view.SetBestBlock(InsecureRand256());
+    view.SetBestBlock(m_rng.rand256());
     BOOST_CHECK(view.Flush());
     print_view_mem_usage(view);