samples: fs: zms: Update to showcase 64 bit ID support

ZMS IDs are not necessarily 32 bit anymore, so the sample ought to
reflect that.

When the sample is built with CONFIG_ZMS_ID_64BIT=y, the KEY_VALUE_ID
will use a 64 bit value, chosen so that it would conflict with CNT_ID
only if 64 bit IDs were not handled properly.

Signed-off-by: Grzegorz Swiderski <grzegorz.swiderski@nordicsemi.no>