Increase message log window width, disable overflow menu (GTK client) (#3971)

* Disable GTK 3 toolbars overflow menu

This prevents the toolbar from hiding its items when they don't fit. Not
an issue with GTK 4 where there's no dedicated toolbar widget and
associated logic.

* Increase default message log window width

gtk/ui/gtk3/MainWindow.ui

@@ -14,6 +14,7 @@
           <object class="GtkToolbar" id="toolbar">
             <property name="visible">True</property>
             <property name="can-focus">False</property>
+            <property name="show-arrow">False</property>
             <child>
               <object class="GtkToolButton" id="open_file_button">
                 <property name="visible">True</property>

gtk/ui/gtk3/MessageLogWindow.ui

@@ -6,7 +6,7 @@
     <property name="can-focus">False</property>
     <property name="title" translatable="yes">Message Log</property>
     <property name="role">message-log</property>
-    <property name="default-width">560</property>
+    <property name="default-width">750</property>
     <property name="default-height">350</property>
     <child>
       <object class="GtkBox" id="window_layout">
@@ -17,6 +17,7 @@
           <object class="GtkToolbar" id="toolbar">
             <property name="visible">True</property>
             <property name="can-focus">False</property>
+            <property name="show-arrow">False</property>
             <child>
               <object class="GtkToolButton" id="save_as_button">
                 <property name="visible">True</property>

gtk/ui/gtk4/MessageLogWindow.ui

@@ -3,7 +3,7 @@
   <requires lib="gtk" version="4.0"/>
   <object class="GtkWindow" id="MessageLogWindow">
     <property name="title" translatable="1">Message Log</property>
-    <property name="default-width">560</property>
+    <property name="default-width">750</property>
     <property name="default-height">350</property>
     <property name="child">
       <object class="GtkBox" id="window_layout">