Moderator note: Moved to the Availability : HA & FT area
Basically , it can reside on same cluster . HA failover is not dependent on vCenter server. During any HA event , your vCenter server will also be restarted on other host like normal virtual machines. Only for setting up HA on a cluster you need vCenter server, not for failover which will be handled by the hosts in the cluster.
You can run VCSA (Appliance mode) inside the same cluster without any concern, but remember this important point: Although you configure the cluster services like HA & DRS from the vCenter management console, but their operations run by ESXi itself (actually HA agent inside the ESXi). Then if you have a failure about VCSA, it will be restarted in another healthy host and management operations of the vCenter will be continue after a safe restart ...
However if you provide and dedicate another cluster for the vCenter, there is same availability requirements that you must consider, include load-balancing and failover needs and also a shared storage ... So in the 2nd cluster ( if you have) you will encounter with same physical and virtual disasters. So I think it's not a perfect solution for vCenter availability.
As the last concept is the vCenter HA feature that is published after release of vSphere 6.5. you must consider VCHA is only available in appliance, however it needs at least to 3-nodes ( 3 hosts) for deploying vCenter Active, Passive and Witness nodes and you need to provide this physical requirement before enabling this availability feature.Please mark my comment as the Correct Answer if this solution resolved your problem