RSDK-9338: add optional parameters in data client

[purplenicole730]

Changes:

• rename some structs for clarity
• add optional parameter structs
• add comments clarifying what happens if a parameter is left empty

Note as to why I didn't put all optional parameters in structs:
At first, I thought I should be putting the optional filter parameters for some of the methods in its own <method>Options struct. Thinking over it some more, I realized these functions could be seen as ones where the user is purposely leaving this parameter nil. This is in line with my discussions with Benji when we first introduced optional parameter structs. It also seemed more straightforward, especially with more clarifying comments.

[jckras]

left a question about the Limit parameter for DataByFilter functions otherwise LGTM! thanks for doing this nicole!