Standardizing built-in extension icon handling (#40606)

Just standardizing built-in extensions to use a `internal sealed class
Icons` for all their non-dynamic icons.

Looks like a LOT of changes, but it's icons all the way down.

src/modules/cmdpal/ext/Microsoft.CmdPal.Ext.TimeDate/Icons.cs

@@ -0,0 +1,20 @@
+// Copyright (c) Microsoft Corporation
+// The Microsoft Corporation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using Microsoft.CommandPalette.Extensions.Toolkit;
+
+namespace Microsoft.CmdPal.Ext.TimeDate;
+
+internal sealed class Icons
+{
+    internal static IconInfo TimeDateExtIcon { get; } = IconHelpers.FromRelativePath("Assets\\TimeDate.svg");
+
+    internal static IconInfo TimeIcon { get; } = new IconInfo("\uE823");
+
+    internal static IconInfo CalendarIcon { get; } = new IconInfo("\uE787");
+
+    internal static IconInfo TimeDateIcon { get; } = new IconInfo("\uEC92");
+
+    internal static IconInfo ErrorIcon { get; } = IconHelpers.FromRelativePaths("Microsoft.CmdPal.Ext.TimeDate\\Assets\\Warning.light.png", "Microsoft.CmdPal.Ext.TimeDate\\Assets\\Warning.dark.png");
+}