swarming: process 5000 bots at once for executor metrics
swarming: process 5000 bots at once for executor metrics

This may mitigate the issue.

_REQUEST_TIMEOUT_SEC is still used to prevent timeout error.

Bug: 1151408
Change-Id: I2510c5516c9d2bbe45b50ca59df383508464994c
Reviewed-on: https://chromium-review.googlesource.com/c/infra/luci/luci-py/+/2691793
Commit-Queue: Junji Watanabe <aaef61ef98ffea505db831f310be2a0eb8492537@google.com>
Reviewed-by: Junji Watanabe <aaef61ef98ffea505db831f310be2a0eb8492537@google.com>
Auto-Submit: Takuto Ikuta <71927f930fca81015e0f496c65cd126ab1a692e3@chromium.org>

luci/luci-py,luci/luci-py,luci/luci-py,luci/luci-py