std/lists: Various changes to lists (RFC nim-lang#303) (nim-lang#16536

)

* Various changes to `lists` (RFC nim-lang#303)

* Removing a non-element is no-op; better tests

* Remove preserves cycles; add appendMove alias; tests.

* Return value for (singly linked) `lists.remove`

* More test for lists.remove

* Moved `lists.append` to the end of the file to see all `add` definitions

* Disable testing js for now

* Use workaround for swap js bug

* Smaller diff

* Undo "silent" deprecation of append

* Correct typo in changelog

Co-authored-by: Timothee Cour <timothee.cour2@gmail.com>

* Remove `appendMoved`

Co-authored-by: Timothee Cour <timothee.cour2@gmail.com>

* Don't remove appendMoved

Co-authored-by: Clyybber <darkmine956@gmail.com>
Co-authored-by: Timothee Cour <timothee.cour2@gmail.com>

changelog.md

@@ -111,6 +111,9 @@ with other backends. see #9125. Use `-d:nimLegacyJsRound` for previous behavior.
 - Added `math.signbit`.
 
 - Removed the optional `longestMatch` parameter of the `critbits._WithPrefix` iterators (it never worked reliably)
+- In `lists`: renamed `append` to `add` and retained `append` as an alias;
+  added `prepend` and `prependMoved` analogously to `add` and `addMoved`;
+  added `remove` for `SinglyLinkedList`s.
 
 
 - Added optional `options` argument to `copyFile`, `copyFileToDir`, and