Consolidate input completion code in preparation for advanced completion strategies (#4639)

Co-authored-by: Rasmus Karlsson <rasmus.karlsson@pajlada.com>

src/widgets/splits/SplitInput.hpp

@@ -22,6 +22,7 @@ class EffectLabel;
 class MessageThread;
 class ResizingTextEdit;
 class ChannelView;
+enum class CompletionKind;
 
 class SplitInput : public BaseWidget
 {
@@ -99,7 +100,7 @@ protected:
     void onTextChanged();
     void updateEmoteButton();
     void updateCompletionPopup();
-    void showCompletionPopup(const QString &text, bool emoteCompletion);
+    void showCompletionPopup(const QString &text, CompletionKind kind);
     void hideCompletionPopup();
     void insertCompletionText(const QString &input_) const;
     void openEmotePopup();