reorg: move JS ops implementations to cli/js/ops/, part 3 (#4302)

Following JS ops were moved to separate files in cli/js/ops directory:
- net
- tls
- fs

cli/js/ops/fs/copy_file.ts

@@ -0,0 +1,29 @@
+// Copyright 2018-2020 the Deno authors. All rights reserved. MIT license.
+import { sendSync, sendAsync } from "../dispatch_json.ts";
+
+/** Synchronously copies the contents and permissions of one file to another
+ * specified path, by default creating a new file if needed, else overwriting.
+ * Fails if target path is a directory or is unwritable.
+ *
+ *       Deno.copyFileSync("from.txt", "to.txt");
+ *
+ * Requires `allow-read` permission on fromPath.
+ * Requires `allow-write` permission on toPath. */
+export function copyFileSync(fromPath: string, toPath: string): void {
+  sendSync("op_copy_file", { from: fromPath, to: toPath });
+}
+
+/** Copies the contents and permissions of one file to another specified path,
+ * by default creating a new file if needed, else overwriting. Fails if target
+ * path is a directory or is unwritable.
+ *
+ *       await Deno.copyFile("from.txt", "to.txt");
+ *
+ * Requires `allow-read` permission on fromPath.
+ * Requires `allow-write` permission on toPath. */
+export async function copyFile(
+  fromPath: string,
+  toPath: string
+): Promise<void> {
+  await sendAsync("op_copy_file", { from: fromPath, to: toPath });
+}