Synthesis and evaluation of antimicrobial and anticonvulsant activities of some new 3-(2{5-aryl-1,3,4-oxadiazol-2-yl/4-carbethoxy-methylthiazol-2-yl)imino-4-thiazolidiinon-5ylidene)-5-substituted/nonsubstituted 1H-indole-2-ones and investigation of their structure-activity relationships