Use re-exported types in examples instead of aws-smithy-types (#3105)

Some of the examples were using types from `aws-smithy-types` instead of
the re-exported ones from the generated SDKs. As a guideline, it is
preferred to use re-exported types rather than directly depending on
underlying crates.

Co-authored-by: Fahad Zubair <fahadzub@amazon.com>