feat(node:fs): add `cp`/`cpSync`/`promises.cp` + async `copyFile` (#4340)

* half working disaster code

* this

* async copyFile

* .

* its failing symlink tests

* asdfg

* asdf

* hmm

* okay i think ti works

* small edits

* fix test on linux

* i hate atomics / atomics hate me back <3

* add a message in the builtins bundler that 0.8 is needed. it breaks on older versions lol.

* fixed

* rebase

1 files changed, 13 insertions, 1 deletions

diff --git a/src/js/private.d.ts b/src/js/private.d.ts
index 854d07c2e..80c22bd51 100644
--- a/src/js/private.d.ts
+++ b/src/js/private.d.ts
@@ -27,7 +27,7 @@ interface BunFSWatcher {
    */
   unref(): void;
 }
-type BunFS = Omit<typeof import("node:fs"), "watch"> & {
+type BunFS = Omit<typeof import("node:fs") & typeof import("node:fs/promises"), "watch" | "cp" | "cpSync"> & {
   /**
    * Watch for changes on `filename`, where `filename` is either a file or a
    * directory.
@@ -87,6 +87,18 @@ type BunFS = Omit<typeof import("node:fs"), "watch"> & {
    * @param filename A path to a file or directory. If a URL is provided, it must use the `file:` protocol.
    */
   watch(filename: string, listener?: BunWatchListener<string>): BunFSWatcher;
+
+  // internal api is for fs.cp and fs.cpSync that is limited to a few options.
+  // there is a js implementation for options like `filter` in `src/js/internal/fs/cp*`
+  cpSync(
+    source: string,
+    dest: string,
+    recursive?: boolean,
+    errorOnExist?: boolean,
+    force?: boolean,
+    mode?: number,
+  ): void;
+  cp(source: string, dest: string, recursive?: boolean, errorOnExist?: boolean, force?: boolean, mode?: number): void;
 };
 
 declare module "bun" {