Refactor SplitHeader class (#4276)

* Flatten static functions in anonymous namespace

* SplitHeader ctor: Rename param

* Header: Remove unnecessary `virtual`s

* auto ptr where possible

* Add curly braces

* Comment twitch room modes

* Treat roomModes->slowMode as an integer

* Remove unused `this` from lambdas

* Add `unsigned int` overload for localizeNumbers

* Move thumbnail max age to a constexpr static & set explicit types

* Explicitly use `QObject::connect`

* Use `empty()` instead of `size()`

* Name unused parameters

* Move moderation action refreshing logic from SplitHeader to Split

src/util/Helpers.cpp

@@ -168,6 +168,12 @@ QString localizeNumbers(const int &number)
     return locale.toString(number);
 }
 
+QString localizeNumbers(unsigned int number)
+{
+    QLocale locale;
+    return locale.toString(number);
+}
+
 QString kFormatNumbers(const int &number)
 {
     return QString("%1K").arg(number / 1000);