update: retry config rfc status (#817)

RFC: Retry Behavior

============================

> Status: RFC

> Status: Implemented

For a summarized list of proposed changes, see the [Changes Checklist](#changes-checklist) section.

Changes checklist

-----------------

- [ ] Create new Kotlin decorator `RetryConfigDecorator`

- [x] Create new Kotlin decorator `RetryConfigDecorator`

  - Based on [RegionDecorator.kt](https://github.com/awslabs/smithy-rs/blob/main/aws/sdk-codegen/src/main/kotlin/software/amazon/smithy/rustsdk/RegionDecorator.kt)

  - This decorator will live in the `codegen` project because it has relevance outside of the SDK

- [ ] **Breaking changes:**

  - [ ] Rename `aws_smithy_client::retry::Config` to `StandardRetryConfig`

  - [ ] Rename `aws_smithy_client::retry::Config::with_max_retries` method to `with_max_attempts` in order to follow AWS convention

  - [ ] Passing 0 to `with_max_attempts` will panic with a helpful, descriptive error message

- [ ] Create non-exhaustive `aws_types::retry_config::RetryConfig` enum wrapping structs that represent specific retry behaviors

  - [ ] A `NoRetry` variant that disables retries. Doesn't wrap a struct since it doesn't need to contain any data

  - [ ] A `Standard` variant that enables the standard retry behavior. Wraps a `StandardRetryConfig` struct.

- [ ] Create `aws_config::meta::retry_config::RetryConfigProviderChain`

- [ ] Create `aws_config::meta::retry_config::ProvideRetryConfig`

- [ ] Create `EnvironmentVariableMaxAttemptsProvider` struct

  - This decorator will live in the `codegen` project because it has relevance outside the SDK

- [x] **Breaking changes:**

  - [x] Rename `aws_smithy_client::retry::Config` to `StandardRetryConfig`

  - [x] Rename `aws_smithy_client::retry::Config::with_max_retries` method to `with_max_attempts` in order to follow AWS convention

  - [x] Passing 0 to `with_max_attempts` will panic with a helpful, descriptive error message

- [x] Create non-exhaustive `aws_types::retry_config::RetryConfig` enum wrapping structs that represent specific retry behaviors

  - [x] A `NoRetry` variant that disables retries. Doesn't wrap a struct since it doesn't need to contain any data

  - [x] A `Standard` variant that enables the standard retry behavior. Wraps a `StandardRetryConfig` struct.

- [x] Create `aws_config::meta::retry_config::RetryConfigProviderChain`

- [x] Create `aws_config::meta::retry_config::ProvideRetryConfig`

- [x] Create `EnvironmentVariableMaxAttemptsProvider` struct

  - Setting AWS_MAX_ATTEMPTS=0 and trying to load from env will panic with a helpful, descriptive error message

- [ ] Add `retry_config` method to `aws_config::ConfigLoader`

- [ ] Update `AwsFluentClientDecorator` to correctly configure the max retry attempts of its inner `aws_hyper::Client` based on the passed-in `Config`

- [ ] Add tests

  - [ ] Test that setting retry_config to 1 disables retries

  - [ ] Test that setting retry_config to `n` limits retries to `n` where `n` is a non-zero integer

  - [ ] Test that correct precedence is respected when overriding retry behavior in a service-specific config

  - [ ] Test that correct precedence is respected when overriding retry behavior in a shared config

  - [ ] Test that creating a config from env if AWS_MAX_ATTEMPTS=0 will panic with a helpful, descriptive error message

  - [ ] Test that setting invalid `max_attempts=0` with a `StandardRetryConfig` will panic with a helpful, descriptive error message

- [x] Add `retry_config` method to `aws_config::ConfigLoader`

- [x] Update `AwsFluentClientDecorator` to correctly configure the max retry attempts of its inner `aws_hyper::Client` based on the passed-in `Config`

- [x] Add tests

  - [x] Test that setting retry_config to 1 disables retries

  - [x] Test that setting retry_config to `n` limits retries to `n` where `n` is a non-zero integer

  - [x] Test that correct precedence is respected when overriding retry behavior in a service-specific config

  - [x] Test that correct precedence is respected when overriding retry behavior in a shared config

  - [x] Test that creating a config from env if AWS_MAX_ATTEMPTS=0 will panic with a helpful, descriptive error message

  - [x] Test that setting invalid `max_attempts=0` with a `StandardRetryConfig` will panic with a helpful, descriptive error message