feat!: Retry overhaul

[jbelkins]

Issue #

#699 (standard architecture)
#338 (retry behavior 2.0 SEP)

Description of changes

Service client configuration

Service client configuration has been moved from code-generation to client runtime, simplifying generated code immensely.
Overall code generated for the SDK is down ~45,000 lines as a result of this change. The new configuration type mostly shares the same public interface as existing configuration types, so although this is technically a breaking change, it should have no effect on most existing clients.

• AWSClientConfiguration serves as the configuration for all AWS services.
• Each service now code-generates only a small, service-specific structure with the service's custom config fields.
• Code-generated protocols for configuration objects served no purpose and are eliminated.
• Added retryStrategyOptions (from the matching PR in smithy-swift) for configuration of retry

Follow-up

There are two retry features that will be added in follow-up PRs:

• Expose the configuration settings for retry
• Custom error handling for AWS service errors

New/existing dependencies impact assessment, if applicable

No new dependencies were added to this change.

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.