Raise global max hosts limit and distro limits

After PM-1607 and PM-1439, we should raise the global max hosts limit. We should also consider raising distro max hosts limits. We may wish to do this over several days, and only raise it again when we validate that we haven't hit some bottleneck. Bottlenecks could include third-party limits (probably AWS) and our own limits (of Evergreen's backing database, or the log storage service).