Add excluded_regions to POST/PUT AWS lib

[sabiurr]

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What does this PR do?

Adds excluded_regions field to AWS API client library for create/update. This will store excluded regions as part of AWS account data in integration config, which will be excluded by AWS crawlers from metric collection

https://datadoghq.atlassian.net/browse/AWS-344

Description of the Change

Updating docs to show excluded_regions

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• Feature or bug fix MUST have appropriate tests (unit, integration, etc...)
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[jirikuncar]

I have updated the cassette using following steps:

1. remove old cassette rm tests/integration/api/cassettes/TestAwsIntegration.test_update.yaml
2. record pytest --vcr-record=all tests/integration/api/test_aws_integration.py -vvv -k test_update
3. verify pytest --vcr-record=none tests/integration/api/test_aws_integration.py -vvv -k test_update

[jirikuncar]

/azp run DataDog.datadogpy.integration

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