This was using some conditional context read and dbg_curr_thread checks,
we can just read the context of the selected thread and write it back as
needed.

Also, packet_reply_register_hex_to was using gdbctx->context, which is
not always the context we want to read.

We still need to keep changes in sync with gdbctx->context as it may be
still be used for step / continue, but step / continue doesn't work well
and we will rewrite it later.
Signed-off-by: Rémi Bernon <rbernon@codeweavers.com>
Signed-off-by: Alexandre Julliard <julliard@winehq.org>