Update HAProxy External guidance for 25k and 50k environments
With the recent switch to using a larger target file in the tests this has had a knock on effect on the large environments, 25k and 50k, with their external load balancer specs.
Essentially with the larger file (640kb) HAProxy now needs to handle larger file downloads at large scales. For this kind of thing HAProxy will usually require more CPU as it's streaming and decoding files (since gzip compression is on).
As such it's been discovered that the advised specs for HAProxy for these two environments with more representative file sizes are underspecced and need to be bumped up from n1-highcpu-2
to n1-highcpu-4
(25k) and n1-highcpu-8
(50k). This in turn makes them consistent with the Internal load balancer recommendations.