1193752 - Make trigger-bot trigger jobs on waves

Status: NEW

(Testing :: General, defect)

Description

[Armen [:armenzg]]

Currently trigger-bot will trigger as many jobs as requested with --rebuild

In this push, Ryan did not use --rebuild since he did not want all 50 jobs to be scheduled at once.
https://treeherder.mozilla.org/#/jobs?repo=try&revision=f7a8891b6e57

Ryan mentions: "The problem with --rebuild is that it schedules everything in one mass dump. I try to trigger 50 or so at a time to run them in waves so as to be slightly less obnoxious about those kind of runs (i.e. not tying up the entire slave pool)."

I proposed using a syntax like this: --waves 5 --rebuild 50
However, I believe that it should be the default behaviour.
Perhaps we want to allow overwrite the default --waves value.

We could also refine this and *not* use the waves behaviour for unbound pools of machine (e.g. EC2 linux pools).