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

extensions/azurecore/resources/dark/add_inverse.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:#252526;}.icon-canvas-transparent{opacity:0;}.icon-vs-bg{fill:#c5c5c5;}</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/azurecore/resources/dark/filter_inverse.svg

@@ -1 +0,0 @@
-<svg id="Layer_1" data-name="Layer 1" xmlns="http://www.w3.org/2000/svg" viewBox="0 0 16 16"><defs><style>.cls-1{font-size:12px;font-family:FullMDL2Assets, Full MDL2 Assets;}.cls-1,.cls-2{fill:#fff;}</style></defs><title>filter_inverse_16x16</title><text class="cls-1" transform="translate(0.03 12.1)"> </text><path class="cls-2" d="M.05,1.63H16V3.33l-6,6v6.27H6V9.31l-6-6ZM15,2.91V2.62H1v.29l6,6v5.69H9V8.89Z"/></svg>

extensions/azurecore/resources/dark/refresh_inverse.svg

@@ -1,4 +0,0 @@
-<svg width="16" height="16" viewBox="0 0 16 16" fill="none" xmlns="http://www.w3.org/2000/svg">
-<path fill-rule="evenodd" clip-rule="evenodd" d="M5.56253 2.51574C3.46348 3.45007 2 5.55411 2 7.99996C2 11.3137 4.68629 14 8 14C11.3137 14 14 11.3137 14 7.99996C14 5.32516 12.2497 3.05916 9.83199 2.28479L9.52968 3.23829C11.5429 3.88451 13 5.77207 13 7.99996C13 10.7614 10.7614 13 8 13C5.23858 13 3 10.7614 3 7.99996C3 6.31101 3.83742 4.81764 5.11969 3.91242L5.56253 2.51574Z" fill="#C5C5C5"/>
-<path fill-rule="evenodd" clip-rule="evenodd" d="M5 3H2V2H5.5L6 2.5V6H5V3Z" fill="#C5C5C5"/>
-</svg>