Increase Bitbucket response size to reduce IO

Bitbucket page sizes can be set by the caller.
The default is 50 items per page, but we can increase this to 100
(max), which will halve the number of API calls needed on large
teams.

Note that we can't set it to an even higher value, because
Bitbucket will reject pagelen values that exceed its max (100) and
return a 400 Bad Request.