itest: add fundMax with maxChanSize test

Add integration test to verify that fundMax uses the protocol-level
maximum channel size instead of the user-configured maxChanSize. The
test uses a table-driven approach to cover both non-wumbo and wumbo
scenarios, creating nodes with restrictive maxChanSize (5M sats) and
verifying that fundMax still creates channels at the protocol maximum.

itest/list_on_test.go

@@ -567,6 +567,10 @@ var allTestCases = []*lntest.TestCase{
 		Name:     "channel fundmax anchor reserve",
 		TestFunc: testChannelFundMaxAnchorReserve,
 	},
+	{
+		Name:     "channel fundmax maxchansize",
+		TestFunc: testChannelFundMaxMaxChanSize,
+	},
 	{
 		Name:     "htlc timeout resolver extract preimage remote",
 		TestFunc: testHtlcTimeoutResolverExtractPreimageRemote,