Here is how you can run an ASA Cluster and Active/ACtive Failover in GNS3:
I did not make these files but I will share them here:
Download the .gns3a appliance and load it into GNS3
Unzip the .7z file and select the hard drive when loading the appliance
https://upw.io/3tp/ASA-Cluster-Appliance.gns3a https://upw.io/3to/ASA_with_clustering-915-16-Clustering_Security_Contexts_Enabled.7z