Swift - S3 MVP examples

[brmur]

• [x] Add scenario per epic
• [x] Add tests for scenario
• [ ] Add single api examples per epic
• [ ] Add tests for single API examples
• [ ] Add S3 Readme. See https://github.com/awsdocs/aws-doc-sdk-examples/tree/main/javascriptv3/example_code/s3 for an example.

Also refer to https://github.com/awsdocs/aws-doc-sdk-examples/wiki/Cross-service-example-guidelines

Related pull requests:

• #3358
• #3363

[shepazon]

s3-basics (scenario) example is done and now working on getting tests finished up for it.