Add HTTP-specific retry options to azure-functions-durable v2 call_http

Add configurable, durable HTTP failure retries to the azure-functions-durable v2 compatibility package in this repository. This is the Python v2 follow-up to Azure/azure-functions-durable-extension#1984, not a request for generic activity retry support.

Current behavior

Checked azure-functions-durable==2.0.0rc1 (azurefunctions-v2.0.0rc1):

• DurableOrchestrationContext.call_http(method, uri, content=None, headers=None, token_source=None, is_raw_str=False) has no HTTP retry parameter and schedules the built-in HTTP polling sub-orchestration.
• DurableHttpRequest neither accepts nor serializes a retry policy or retryable-status-code list.
• builtin_http_activity returns HTTP error responses rather than treating selected statuses as retryable failures.
• The polling orchestrator calls activities without a retry policy and repeats only for HTTP 202 responses with a Location header.

This package executes HTTP through worker-side built-ins rather than the extension's native HTTP action. Retry support must be implemented in that worker path, not just added to a host-bound JSON field.

Acceptance Criteria

• Expose HTTP-specific retry configuration on call_http, including first retry interval, maximum attempts, backoff coefficient, maximum retry interval, retry timeout, and retryable HTTP status codes.
• Carry the configuration through the request model/serialization and apply durable retries to selected HTTP statuses and retryable transport failures.
• Define and document status-code defaults consistent with .NET HttpRetryOptions (an omitted/empty status-code list retries 4xx/5xx responses when a retry policy is supplied).
• Preserve existing behavior when retry options are omitted, and keep HTTP 202 polling distinct from failure retries.
• Add coverage for retry-then-success, exhausted attempts, excluded status codes, backoff/timeout limits, replay, and interaction with 202 polling.
• Document usage and any intentional differences from .NET HTTP retry semantics.

Related

• Original cross-language tracker: Azure/azure-functions-durable-extension#1984.
• Equivalent Node v4 work: microsoft/durabletask-js#367.
• .NET HttpRetryOptions reference implementation.

Start with DurableOrchestrationContext.call_http and the HTTP worker path in azure-functions-durable/azure/durable_functions/http/models.py and builtin.py. Trace request serialization and the polling orchestrator before comparing the .NET HttpRetryOptions semantics. Done means configured failure retries, preserved 202 polling and no-option behavior, documented usage, and tests for success, exhaustion, exclusions, limits, replay, and polling interaction.