[dataset] add message length checks when processing MGMT_SET.req (#2671)
[dataset] add message length checks when processing MGMT_SET.req (#2671)

Credit to OSS-Fuzz.
georgecpr/openthread,mszczodrak/openthread,chshu/openthread,erja-gp/openthread,librasungirl/openthread,srickardti/openthread,abtink/openthread,turon/openthread,srickardti/openthread,librasungirl/openthread,georgecpr/openthread,LeZhang2016/openthread,LeZhang2016/openthread,mszczodrak/openthread,abtink/openthread,chshu/openthread,gandreello/openthread,openthread/openthread,pvanhorn/openthread,gandreello/openthread,georgecpr/openthread,librasungirl/openthread,gandreello/openthread,abtink/openthread,chshu/openthread,pvanhorn/openthread,mszczodrak/openthread,jwhui/openthread,LeZhang2016/openthread,pvanhorn/openthread,LeZhang2016/openthread,bukepo/openthread,pvanhorn/openthread,srickardti/openthread,mszczodrak/openthread,georgecpr/openthread,openthread/openthread,abtink/openthread,bukepo/openthread,turon/openthread,pvanhorn/openthread,georgecpr/openthread,LeZhang2016/openthread,jwhui/openthread,gandreello/openthread,openthread/openthread,lanyuwen/openthread,erja-gp/openthread,turon/openthread,gandreello/openthread,erja-gp/openthread,librasungirl/openthread,erja-gp/openthread,jwhui/openthread,srickardti/openthread,mszczodrak/openthread,lanyuwen/openthread,mszczodrak/openthread,georgecpr/openthread,erja-gp/openthread,bukepo/openthread,chshu/openthread,turon/openthread,erja-gp/openthread,LeZhang2016/openthread,chshu/openthread,openthread/openthread,bukepo/openthread,chshu/openthread,lanyuwen/openthread,jwhui/openthread,gandreello/openthread,pvanhorn/openthread,lanyuwen/openthread,lanyuwen/openthread,lanyuwen/openthread