waitForGatewayPublish takes 10+ seconds

[mkysel]

Publishing a payload to staging takes 15 seconds on average with many requests timing out after 30.

After adding additional metrics and logging #1510 we can narrow down the issue to waitForGatewayPublish

This operation should not take more than 100ms.

In the screenshot we see everything at 10s. This is because the default histogram buckets max out at 10s.