Parallel describe

[tjkirch]

Description of changes:

Add info logging before service requests to help explain timing

pubsys: check for copied AMIs in parallel
    
We were waiting on the get_ami_id calls serially which led to an unnecessary
increase in runtime when we increase region count.

Testing done:

Before, it takes 16 seconds for 16 regions consistently, with less information shown:

18:45:48 [INFO] Found ami-12345 available in us-west-2
18:46:04 [INFO] Starting copy from us-west-2 to ap-northeast-1

After, it takes 7 seconds for 16 regions consistently, and shows useful information between calls:

19:06:43 [INFO] Found ami-23456 available in us-west-2
19:06:43 [INFO] Getting account IDs for target regions so we can grant access to copy source AMI
19:06:46 [INFO] Checking whether AMIs already exist in target regions
19:06:50 [INFO] Starting copy from us-west-2 to ap-northeast-1

Terms of contribution:

By submitting this pull request, I agree that this contribution is dual-licensed under the terms of both the Apache License, version 2.0, and the MIT license.

[zmrow]

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