feat: Add swift bindings for `ecs-env`

[dayaffe]

Describe the feature

Bind out to swift this new function in C layer https://github.com/awslabs/aws-c-auth/blob/48d647bf43f8872e4dc5ec6343b0c5974195fbdd/include/aws/auth/credentials.h#L1066 for resolving ECS credentials from environment to new function ecs-env.

Use Case

ECS Credential Provider in AWS SDK for Swift

Proposed Solution

No response

Other Information

No response

Acknowledgements

• I may be able to implement this feature request
• This feature might incur a breaking change