Update trigger_wait_ac_task.py to use GCS instead of webhooks
Update trigger_wait_ac_task.py to use GCS instead of webhooks

* Add more frequent task status updates.
* Add exponential retries when hitting GCS.

Bug: skia:8087
Bug: skia:8387
Change-Id: Iff8320b88999fde53c1ad4814dc9243ebd8138a8
Reviewed-on: https://skia-review.googlesource.com/155163
Commit-Queue: Ravi Mistry <9fa2e7438b8cb730f96b74865492597170561628@google.com>
Reviewed-by: Eric Boren <0e499112533c8544f0505ea0d08394fb5ad7d8fa@google.com>

Hikari-no-Tenshi/android_external_skia,aosp-mirror/platform_external_skia,rubenvb/skia,aosp-mirror/platform_external_skia,google/skia,HalCanary/skia-hc,aosp-mirror/platform_external_skia,google/skia,aosp-mirror/platform_external_skia,HalCanary/skia-hc,google/skia,HalCanary/skia-hc,rubenvb/skia,Hikari-no-Tenshi/android_external_skia,rubenvb/skia,aosp-mirror/platform_external_skia,aosp-mirror/platform_external_skia,HalCanary/skia-hc,google/skia,Hikari-no-Tenshi/android_external_skia,Hikari-no-Tenshi/android_external_skia,HalCanary/skia-hc,aosp-mirror/platform_external_skia,rubenvb/skia,google/skia,aosp-mirror/platform_external_skia,aosp-mirror/platform_external_skia,rubenvb/skia,Hikari-no-Tenshi/android_external_skia,rubenvb/skia,google/skia,rubenvb/skia,google/skia,HalCanary/skia-hc,HalCanary/skia-hc,google/skia,Hikari-no-Tenshi/android_external_skia,HalCanary/skia-hc,google/skia,Hikari-no-Tenshi/android_external_skia,google/skia,rubenvb/skia,Hikari-no-Tenshi/android_external_skia,aosp-mirror/platform_external_skia,HalCanary/skia-hc,rubenvb/skia,rubenvb/skia,HalCanary/skia-hc