chore(Transfer, TypeScript): fix event list response types

[theroncross]

The Transfer service returns a total property from both the user and endpoint-manager /event_list endpoints. This value is not included in some other responses that use offset paging.

Similarly, the event_list responses do not include has_next_page, so I've marked it as optional.

Finally, the DATA_TYPE property from this endpoint was not quite correct.

[jbottigliero]

Just want to clarify, from Transfer's end total is related to the offset paging specifically and doesn't happen to just be included on these resources?

[theroncross]

total is included in /task_list responses, but not /endpoint_search responses, both of which use offset paging.

edit: Apparently the total is expensive to calculate and will not be included in this response in the v2 api. I let the team know that it was useful to us, so we may end up with another way to access the total.