remove icon files and use codicons for extensions (#9305)

extensions/cms/resources/light/add.svg

@@ -1 +0,0 @@
-<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 16 16"><defs><style>.icon-canvas-transparent,.icon-vs-out{fill:#f6f6f6;}.icon-canvas-transparent{opacity:0;}.icon-vs-bg{fill:#424242;}</style></defs><title>add</title><g id="canvas"><path class="icon-canvas-transparent" d="M16,16H0V0H16Z"/></g><g id="outline" style="display: none;"><path class="icon-vs-out" d="M14,6v4H10v4H6V10H2V6H6V2h4V6Z"/></g><g id="iconBg"><path class="icon-vs-bg" d="M13,7V9H9v4H7V9H3V7H7V3H9V7Z"/></g></svg>

extensions/cms/resources/light/refresh.svg

@@ -1 +0,0 @@
-<svg xmlns="http://www.w3.org/2000/svg" width="16" height="16"><path d="M13.451 5.609l-.579-.939-1.068.812-.076.094c-.335.415-.927 1.341-1.124 2.876l-.021.165.033.163.071.345c0 1.654-1.346 3-3 3-.795 0-1.545-.311-2.107-.868-.563-.567-.873-1.317-.873-2.111 0-1.431 1.007-2.632 2.351-2.929v2.926s2.528-2.087 2.984-2.461h.012l3.061-2.582-4.919-4.1h-1.137v2.404c-3.429.318-6.121 3.211-6.121 6.721 0 1.809.707 3.508 1.986 4.782 1.277 1.282 2.976 1.988 4.784 1.988 3.722 0 6.75-3.028 6.75-6.75 0-1.245-.349-2.468-1.007-3.536z" fill="#F6F6F6"/><path d="M12.6 6.134l-.094.071c-.269.333-.746 1.096-.91 2.375.057.277.092.495.092.545 0 2.206-1.794 4-4 4-1.098 0-2.093-.445-2.817-1.164-.718-.724-1.163-1.718-1.163-2.815 0-2.206 1.794-4 4-4l.351.025v1.85s1.626-1.342 1.631-1.339l1.869-1.577-3.5-2.917v2.218l-.371-.03c-3.176 0-5.75 2.574-5.75 5.75 0 1.593.648 3.034 1.695 4.076 1.042 1.046 2.482 1.694 4.076 1.694 3.176 0 5.75-2.574 5.75-5.75-.001-1.106-.318-2.135-.859-3.012z" fill="#424242"/></svg>