Missing proxy support in AWSCRTHTTPClient → blocks aws_sdk_bedrock_runtime in private VPCs

Please let me know if I'm missing something When using `aws_sdk_bedrock_runtime` to invoke Amazon Nova Sonic in a private VPC (us-west-2), the HTTP stack cannot honor HTTP_PROXY / HTTPS_PROXY because the CRT-based HTTP client does not expose any proxy configuration.

This makes `aws_sdk_bedrock_runtime` unusable in environments where all outbound internet access must go through a proxy (e.g., ECS Fargate in private subnets without NAT or VPC endpoint).

**Application creates a Bedrock client:**

```
crt_http_client = create_crt_http_client(PROXY_URL if not IS_DEV else None)

bedrock_nova_sonic_config = BedrockConfig(
endpoint_uri=f"https://bedrock-runtime.{ONLY_AVAILABLE_REGION_FOR_AWS_NOVA}.amazonaws.com",
region=ONLY_AVAILABLE_REGION_FOR_AWS_NOVA,
aws_credentials_identity_resolver=EnvironmentCredentialsResolver(),
http_auth_scheme_resolver=HTTPAuthSchemeResolver(),
http_auth_schemes={"aws.auth#sigv4": SigV4AuthScheme()},
http_client=crt_http_client,
)
bedrock_client = BedrockRuntimeClient(bedrock_nova_sonic_config)
```

**That `crt_http_client` is always an instance of:**
`from smithy_http.aio.crt import AWSCRTHTTPClient`

**Which in turn requires AWSCRTHTTPClientConfig:**
```
class AWSCRTHTTPClientConfig(http_interfaces.HTTPClientConfiguration):
def __post_init__(self) -> None:
_assert_crt()
And the actual client implementation:
class AWSCRTHTTPClient(http_aio_interfaces.HTTPClient):
_HTTP_PORT = 80
_HTTPS_PORT = 443

def __init__(self, eventloop=None, client_config=None):
_assert_crt()
self._config = client_config or AWSCRTHTTPClientConfig()
self._eventloop = eventloop or _AWSCRTEventLoop()
self._client_bootstrap = self._eventloop.bootstrap
self._tls_ctx = crt_io.ClientTlsContext(crt_io.TlsContextOptions())
self._socket_options = crt_io.SocketOptions()
self._connections = {}
```

**The only config type available is:**

```
@dataclass(kw_only=True)
class HTTPClientConfiguration:
"""Client-level HTTP configuration.

:param force_http_2: Whether to require HTTP/2.
"""
force_http_2: bool = False

```
There is no field for proxy configuration, nor does **AWSCRTHTTPClient** internally handle HTTP_PROXY / HTTPS_PROXY.
The underlying call in _build_new_connection goes directly to crt_http.HttpClientConnection.new(...) with just host_name, port, socket_options, and tls_connection_options.

Please add first-class proxy support to smithy-http’s `AWSCRTHTTPClient`.

Bắt đầu với AWSCRTHTTPClientConfig và AWSCRTHTTPClient trong smithy-http, sau đó theo dõi _build_new_connection và lệnh gọi đến crt_http.HttpClientConnection.new(...). Xác định cấu hình proxy nên được biểu diễn và truyền qua CRT client như thế nào. Được xem là hoàn tất khi AWSCRTHTTPClient có thể sử dụng HTTP_PROXY/HTTPS_PROXY hoặc các thiết lập proxy tương đương được hỗ trợ trực tiếp cho các Bedrock client trong các VPC riêng tư.

Do mô hình lập chỉ mục viết ra từ nội dung của issue.