core, ethclient/gethclient: improve flaky tests (#25918)

* ethclient/gethclient: improve time-sensitive flaky test

* eth/catalyst: fix (?) flaky test

* core: stop blockchains in tests after use

* core: fix dangling blockchain instances

* core: rm whitespace

* eth/gasprice, eth/tracers, consensus/clique: stop dangling blockchains in tests

* all: address review concerns

* core: goimports

* eth/catalyst: fix another time-sensitive test

* consensus/clique: add snapshot test run function

* core: rename stop() to stopWithoutSaving()

Co-authored-by: Felix Lange <fjl@twurst.com>

ethclient/gethclient/gethclient_test.go

@@ -106,10 +106,6 @@ func TestGethClient(t *testing.T) {
 		name string
 		test func(t *testing.T)
 	}{
-		{
-			"TestAccessList",
-			func(t *testing.T) { testAccessList(t, client) },
-		},
 		{
 			"TestGetProof",
 			func(t *testing.T) { testGetProof(t, client) },
@@ -132,8 +128,15 @@ func TestGethClient(t *testing.T) {
 			"TestCallContract",
 			func(t *testing.T) { testCallContract(t, client) },
 		},
+		// The testaccesslist is a bit time-sensitive: the newTestBackend imports
+		// one block. The `testAcessList` fails if the miner has not yet created a
+		// new pending-block after the import event.
+		// Hence: this test should be last, execute the tests serially.
+		{
+			"TestAccessList",
+			func(t *testing.T) { testAccessList(t, client) },
+		},
 	}
-	t.Parallel()
 	for _, tt := range tests {
 		t.Run(tt.name, tt.test)
 	}