[luigi617]

Issue #, if available:

Description of changes:
Check that CLI examples run the command they describe and fix existing violations

The description check requires each example to name the file's command, e.g. The following stop-stream-encryption example, but nothing checked that the example actually runs it. kinesis/stop-stream-encryption.rst ran start-stream-encryption and passed.

• Added test_example_command_name to tests/functional/docs/test_examples.py: each example must run the command of its file, such as aws ec2 wait instance-running for ec2/wait/instance-running.rst. Other commands, such as a setup step, are allowed alongside it
• Fixed examples that ran the wrong command: kinesis/stop-stream-encryption.rst, gamelift/stop-fleet-actions.rst, transcribe/delete-medical-vocabulary.rst, greengrassv2/untag-resource.rst, iot/add-thing-to-billing-group.rst, waf-regional/update-ip-set.rst
• Rewrote iot/update-job.rst and iot/describe-audit-suppression.rst, which showed describe-job and describe-audit-task examples
• Removed Example 2 of proton/list-service-instances.rst, which duplicated proton/get-service-instance.rst
• Restructured RDS examples that split a walkthrough into numbered examples of other commands:
  • Moved the cluster and writer instance steps of create-db-shard-group.rst into create-db-cluster.rst and create-db-instance.rst
  • Combined the steps of delete-db-cluster.rst and purchase-reserved-db-instances-offering.rst into one example each
  • Removed the describe-db-shard-groups steps from modify-db-shard-group.rst and reboot-db-shard-group.rst

Testing

• Run pytest tests/functional/docs/test_examples.py -n auto

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