Update scm tree filter icons to use icon font

FYI @joaomoreno

src/vs/workbench/contrib/scm/browser/media/list-dark.svg

-<svg width="16" height="16" viewBox="0 0 16 16" fill="none" xmlns="http://www.w3.org/2000/svg">
-<path d="m1 12v-1h14v1zm0-5h14v1h-14zm14-4v1h-14v-1z" fill="#C5C5C5"/>
-</svg>

src/vs/workbench/contrib/scm/browser/media/list-hc.svg

-<svg width="16" height="16" viewBox="0 0 16 16" fill="none" xmlns="http://www.w3.org/2000/svg">
-<path d="m1 12v-1h14v1zm0-5h14v1h-14zm14-4v1h-14v-1z" fill="white"/>
-</svg>

src/vs/workbench/contrib/scm/browser/media/list-light.svg

-<svg width="16" height="16" viewBox="0 0 16 16" fill="none" xmlns="http://www.w3.org/2000/svg">
-<path d="m1 12v-1h14v1zm0-5h14v1h-14zm14-4v1h-14v-1z" fill="#424242"/>
-</svg>

src/vs/workbench/contrib/scm/browser/media/scmViewlet.css

@@ -7,30 +7,6 @@
 	-webkit-mask: url('scm-activity-bar.svg') no-repeat 50% 50%;
 }
 
-.monaco-workbench .scm-action.toggle-view-mode.list {
-	background: url('list-light.svg') center center no-repeat;
-}
-
-.vs-dark .monaco-workbench .scm-action.toggle-view-mode.list {
-	background: url('list-dark.svg') center center no-repeat;
-}
-
-.hc-black .monaco-workbench .scm-action.toggle-view-mode.list {
-	background: url('list-hc.svg') center center no-repeat;
-}
-
-.monaco-workbench .scm-action.toggle-view-mode.tree {
-	background: url('tree-light.svg') center center no-repeat;
-}
-
-.vs-dark .monaco-workbench .scm-action.toggle-view-mode.tree {
-	background: url('tree-dark.svg') center center no-repeat;
-}
-
-.hc-black .monaco-workbench .scm-action.toggle-view-mode.tree {
-	background: url('tree-hc.svg') center center no-repeat;
-}
-
 .monaco-workbench .viewlet.scm-viewlet .collapsible.header .actions {
 	width: initial;
 	flex: 1;

src/vs/workbench/contrib/scm/browser/media/tree-dark.svg

-<svg width="16" height="16" viewBox="0 0 16 16" fill="none" xmlns="http://www.w3.org/2000/svg">
-<path d="m2 4v-1h4v1zm0 3h8v1h-8zm12 4v1h-12v-1z" fill="#C5C5C5"/>
-</svg>

src/vs/workbench/contrib/scm/browser/media/tree-hc.svg

-<svg width="16" height="16" viewBox="0 0 16 16" fill="none" xmlns="http://www.w3.org/2000/svg">
-<path d="m2 4v-1h4v1zm0 3h8v1h-8zm12 4v1h-12v-1z" fill="white"/>
-</svg>

src/vs/workbench/contrib/scm/browser/media/tree-light.svg

-<svg width="16" height="16" viewBox="0 0 16 16" fill="none" xmlns="http://www.w3.org/2000/svg">
-<path d="m2 4v-1h4v1zm0 3h8v1h-8zm12 4v1h-12v-1z" fill="#424242"/>
-</svg>

src/vs/workbench/contrib/scm/browser/repositoryPanel.ts

@@ -389,8 +389,8 @@ function asTreeElement(node: INode<ISCMResource, ISCMResourceGroup>, incompressi
 }
 
 const enum ViewModelMode {
-	List = 'list',
-	Tree = 'tree'
+	List = 'codicon-filter',
+	Tree = 'codicon-selection'
 }
 
 class ViewModel {