Implement NetClient PushGuiMessage using parameter pack and ScriptInterface::CreateObject from D2080 / b4626359f5 to replace remaining Eval function calls.

Specialize ToJSVal<char[n]> to allow passing string literals as
arguments.
Freeze NetClient GUI messages.
Supersede related c-style casts with static casts.
Remove few unneeded conversions.

Differential Revision: https://code.wildfiregames.com/D2267
Tested: clang 8.0.1, Jenkins

This was SVN commit r22867.

source/network/NetClientTurnManager.cpp

@@ -142,21 +142,12 @@ void CNetClientTurnManager::OnSyncError(u32 turn, const CStr& expectedHash, cons
 
 	LOGERROR("Out-Of-Sync on turn %d\nPlayers: %s\nDumping state to %s", turn, playerNamesString.str().c_str(), oosdumpPath.string8());
 
-	const ScriptInterface& scriptInterface = m_NetClient.GetScriptInterface();
-	JSContext* cx = scriptInterface.GetContext();
-	JSAutoRequest rq(cx);
-
-	JS::RootedValue msg(cx);
-
-	scriptInterface.CreateObject(
-		&msg,
-		"type", std::wstring(L"out-of-sync"),
+	m_NetClient.PushGuiMessage(
+		"type", "out-of-sync",
 		"turn", turn,
 		"players", playerNamesStrings,
 		"expectedHash", expectedHashHex,
 		"hash", Hexify(hash),
 		"path_oos_dump", wstring_from_utf8(oosdumpPath.string8()),
 		"path_replay", wstring_from_utf8(m_Replay.GetDirectory().string8()));
-
-	m_NetClient.PushGuiMessage(msg);
 }