debug: polish HC theme colors

src/vs/workbench/parts/debug/browser/media/debugActionsWidget.css

@@ -47,12 +47,17 @@
 	background-repeat: no-repeat;
 }
 
-.vs-dark .monaco-workbench .debug-actions-widget,
-.hc-black .monaco-workbench .debug-actions-widget {
+.vs-dark .monaco-workbench .debug-actions-widget {
 	background-color: #333;
 	box-shadow: 0 5px 8px #000;
 }
 
+.hc-black .monaco-workbench .debug-actions-widget {
+	background-color: #000;
+	box-shadow: unset;
+	border: 1px solid #6FC3DF;
+}
+
 /* Debug actionbar actions */
 
 .monaco-workbench .debug-actions-widget .debug-action.step-over,

src/vs/workbench/parts/debug/browser/media/debugViewlet.css

@@ -91,11 +91,14 @@
 	cursor: pointer;
 }
 
-.vs-dark .monaco-workbench .monaco-action-bar .start-debug-action-item .configuration .select-box,
-.hc-black .monaco-workbench .monaco-action-bar .start-debug-action-item .configuration .select-box {
+.vs-dark .monaco-workbench .monaco-action-bar .start-debug-action-item .configuration .select-box {
 	background-color: #252526;
 }
 
+.hc-black .monaco-workbench .monaco-action-bar .start-debug-action-item .configuration .select-box {
+	background-color: #000;
+}
+
 .monaco-workbench .monaco-action-bar .start-debug-action-item .configuration.disabled .select-box {
 	opacity: 0.7;
 	font-style: italic;