In Go 1.23, the standard maps.Keys helper was altered relative to xmaps.Keys
to return and iterator, which can be used with slices.Collect.
Also, Go 1.21 added the clear built-in, which replaces xmaps.Clear,
and is semantically more correct with respect to NaNs.
Updates #8632
Updates #12912
Updates #cleanup
Signed-off-by: Joe Tsai <joetsai@digital-static.net>