Update agent.go and handlers.go for 3rd party agent UI support

[0xTriboulet]

Fixed HealthUI and OS Version UI for 3rd party agents.

Havoc/teamserver/pkg/agent/agent.go

	// Updated OS Version handling - 0xtriboulet
	if val, ok := RegisterInfo["OS Version"]; ok {
	    // Assuming val is a string representing the OS version, split it by '.' to get the version parts, 0xtriboulet
	    versionParts := strings.Split(val.(string), ".")
	    OsVersion := make([]int, len(versionParts))
	    for i, part := range versionParts {
		OsVersion[i], _ = strconv.Atoi(part)
	    }
	    agent.Info.OSVersion = getWindowsVersionString(OsVersion)
	}

Havoc/teamserver/pkg/handlers/handlers.go

	// Update Callback time - 0xtriboulet
	if Teamserver.AgentExist(Header.AgentID) {
		Agent.UpdateLastCallback(Teamserver)
	}