Add copyBlob to FilterBlobContainer (#131704)

This makes it possible to hook copy in test.

Author: bcully

server/src/main/java/org/elasticsearch/common/blobstore/support/FilterBlobContainer.java

@@ -121,6 +121,14 @@ public void writeBlobAtomic(OperationPurpose purpose, String blobName, BytesRefe
         delegate.writeBlobAtomic(purpose, blobName, bytes, failIfAlreadyExists);
     }
 
+    @Override
+    public void copyBlob(OperationPurpose purpose, BlobContainer sourceBlobContainer, String sourceBlobName, String blobName, long blobSize)
+        throws IOException {
+        // FsBlobContainer accesses internals of the sourceBlobContainer in copyBlob so it needs the delegate
+        assert sourceBlobContainer instanceof FilterBlobContainer;
+        delegate.copyBlob(purpose, ((FilterBlobContainer) sourceBlobContainer).delegate, sourceBlobName, blobName, blobSize);
+    }
+
     @Override
     public DeleteResult delete(OperationPurpose purpose) throws IOException {
         return delegate.delete(purpose);