R1:a82c3a89144e

Allow Maniphest queries to have configurable page sizes

Summary:
Current page size is `1000`. This is nice to have in some cases, but makes pages slower than necessary in others. Task lists are generally dominated by rendering costs.

For example, my default is "recent tasks", which just lists all tasks ordered by date created. Showing 100 tasks here instead of 1000 makes this several times faster without compromising utility.

I don't want to force the default to 100, though, since sometimes listing…