Allow setting page size separately from limit in `page_cursor()`

[karawoo]

page_cursor() currently has strange behavior where the limit argument controls both the total number of results and the page size, but in different ways.

connectapi/R/connect.R

Line 725 in 1bfa7ea

limit = valid_page_size(limit),

• If limit = Inf, page size is 500 and you get all results
• If limit > 500 & limit < Inf, page size is 500 and you get limit results
• If limit > 0 & limit <= 500, page size is limit and you get limit results

There is no way to, say, set the page size and limit to different values unless limit > 500. We should expose more flexibility here.