Add AssetPassFilterDrop

Planning to use this to drop .svg files from SS14's resources folder. Tiny opt.

RELEASE-NOTES.md

@@ -40,6 +40,7 @@ END TEMPLATE-->
 ### New features
 
 * Added stack-like functions to `ValueList<T>` and added an `AddRange(ReadOnlySpan<T>)` overload.
+* Added new `AssetPassFilterDrop`.
 
 ### Bugfixes
 

Robust.Packaging/AssetProcessing/Passes/AssetPassFilterDrop.cs

@@ -0,0 +1,18 @@
+namespace Robust.Packaging.AssetProcessing.Passes;
+
+/// <summary>
+/// Asset pass that drops all files that match a predicate. Files that do not match are ignored.
+/// </summary>
+public sealed class AssetPassFilterDrop(Func<AssetFile, bool> predicate) : AssetPass
+{
+    public Func<AssetFile, bool> Predicate { get; } = predicate;
+
+    protected override AssetFileAcceptResult AcceptFile(AssetFile file)
+    {
+        // Just do nothing with the file so it gets discarded.
+        if (Predicate(file))
+            return AssetFileAcceptResult.Consumed;
+
+        return base.AcceptFile(file);
+    }
+}