GEOADD - add [CH] [NX|XX] options (#8227)

New command flags similar to what SADD already has.

Co-authored-by: huangwei03 <huangwei03@kuaishou.com>
Co-authored-by: Itamar Haber <itamar@redislabs.com>
Co-authored-by: Oran Agra <oran@redislabs.com>