Adding sts.assume_role() support to resource_sync

[andreivmaksimov]

Issue #, if available: Adding an ability to assume an IAM role in source and destination AWS accounts

Description of changes: Adding --src-role-arn and --dst-role-arn parameters. The --sts-role-arn has been removed.

Testing:

cd utilities/resource_sync
python3 -m venv .venv
source .venv/bin/activate
pip install -r requirements.txt

pytest 

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