Manage auto-scaling and throttling in Elixir N1QL tests

We need to trigger index/query auto-scaling and measure query performance during the auto-scaling process. However, there are several issues we need to resolve first.

• In order to reduce doc loading time and index building time, we need to increase throttling limits. However, it will trigger index auto-scaling during the index building (MB-55679). In our runs, we saw the number of index nodes increased from 2 to 8 during the index building. Therefore, we need to disable auto-scaling. After finishing index building, we need to enable auto-scaling again (CBPS-1145).
• In our current n1ql runs, we see high KV CPU utilization (~80%) (MB-56085/AV-49806). Given the high KV CPU utilization, we won't be able to trigger index/query auto-scaling.
• We increase throttling limit during doc loading and index building and set throttling limit back to default vales (5K) before we start measurement. With the default throttling limit, KV or Index may become the bottleneck first.