UI: Add save button next to replay buffer button

Allows the ability to save replays with a button rather than with the
keyboard if desired.

Closes obsproject/obs-studio#1954

UI/data/themes/Acri.qss

@@ -1044,3 +1044,9 @@ SceneTree#scenes {
     padding-right: 10px;
     margin: 0px;
 }
+
+/* Save replay icon */
+
+* [themeID="replayIconSmall"] {
+    qproperty-icon: url(./Dark/save.svg);
+}

UI/data/themes/Dark.qss

@@ -809,3 +809,9 @@ SceneTree {
 *[gridMode="true"] SceneTree::item:checked {
     background-color: rgb(122,121,122); /* light */
 }
+
+/* Save icon */
+
+* [themeID="replayIconSmall"] {
+    qproperty-icon: url(./Dark/save.svg);
+}

UI/data/themes/Dark/save.svg

@@ -0,0 +1,3 @@
+<svg xmlns="http://www.w3.org/2000/svg" width="8" height="8" viewBox="0 0 8 8" fill="#d2d2d2">
+  <path d="M3 0v3h-2l3 3 3-3h-2v-3h-2zm-3 7v1h8v-1h-8z" />
+</svg>

UI/data/themes/Rachni.qss

@@ -1372,3 +1372,9 @@ SceneTree#scenes {
     qproperty-gridItemWidth: 150;
     qproperty-gridItemHeight: 30;
 }
+
+/* Save icon */
+
+* [themeID="replayIconSmall"] {
+    qproperty-icon: url(./Dark/save.svg);
+}

UI/data/themes/System.qss

@@ -240,3 +240,9 @@ SceneTree {
     qproperty-gridItemWidth: 150;
 	qproperty-gridItemHeight: 24;
 }
+
+/* Save icon */
+
+* [themeID="replayIconSmall"] {
+    qproperty-icon: url(:res/images/save.svg);
+}