Switch to batch calls to fetch assigned and fixed bugs for Bugzilla

[grssam]

Instead of making 2 calls (1 for assigned bugs and 1 for fixed) per user for bugzilla stats, we can club both calls for all (or batch of) users into one single call.

We will still need to make 1 call per user for getting the component information though.

We can even go further ahead and calculate the fixed numbers by summing up the numbers obtained from the components call. This will make the first batch call faster.