chore: Update examples to use latest versions and practices

[bryantbiggs]

Description

• Update examples to use latest engine versions and security group module version (redis does not support latest 7.x versions)
• Update examples to use data source for computing AZs and CIDR ranges
• Deploy examples into eu-west-1 consistent with other module examples (where supported)
• Rename complete example to redis to better reflect intent. Both examples are technically "complete" but demonstrate either engine option
• engine is now required; this has been added to the redis example
• The user names were made unique to allow for both examples to be provisioned at same time, otherwise there was a duplicate resource name conflict

Motivation and Context

• Up to date and consistent

Breaking Changes

• No

How Has This Been Tested?

• I have updated at least one of the examples/* to demonstrate and validate my change(s)
• I have tested and validated these changes using one or more of the provided examples/* projects
• I have executed pre-commit run -a on my pull request

[magreenbaum]

Thank you!