feat(layers): show select parent in every row's hover tools

Select parent is one of the most used row actions, but outside
script-added rows it was reachable only through the "..." menu. Show its
up-arrow first in every element row's hover tools, before insert,
duplicate, delete and the menu button. The root and text rows still have
no tools, so every row that shows it has a parent.

Reserve 130px instead of 106px for the tools, so a hovered row's label
stops short of five buttons. Script-added rows keep select parent as
their only tool.

Author: abose

src/styles/Extn-LayersPanel.less

@@ -34,7 +34,7 @@
 @layers-row-height:     28px;
 @layers-label-min-width: 72px;
 @layers-row-intrinsic-width: 115px;
-@layers-tools-width:    106px;
+@layers-tools-width:    130px;
 @layers-script-tools-width: 34px;
 @layers-mono: ui-monospace, SFMono-Regular, "SF Mono", Menlo, Consolas, monospace;
 @layers-prop-name:      #9cdcfe;
@@ -982,7 +982,7 @@
         padding-right: 0;
     }
 
-    .layers-node:not(.layers-script-node) .layers-action-select-parent,
+    // A script-added element has no source to edit, so select parent is its only tool.
     .layers-node.layers-script-node .layers-node-action:not(.layers-action-select-parent) {
         display: none;
     }