Retry logic for DescribeRegions while creating new account, handling non-empty default vpc v2

[sbkok]

Rebased version with fixes of pull request #238, as proposed in the review comments.
Pushing the changes to the same branch was not enabled, hence fixing it with a separate pull request.

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Original description:

Issues:

when creating a new account, AWS services are not available for some time and bootstrap pipeline and step function fail
when deleting default VPCs, pipeline fails if a VPC is non-empty and stops to delete default VPC in any other regions.

Description of changes:

This code enables ADF to wait for services enablement and retry.
This code handles exception on non-empty VPC and continues to delete VPCs in other regions.

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[deltagarrett]

LGTM

[krisnielander]

LGTM2