feat(tools): expose httpx_client_factory on RestApiTool and OpenAPITo…

[darshil3011]

…olset

Mirror the pattern merged for MCP in #2997 (StreamableHTTPConnectionParams. httpx_client_factory) on the OpenAPI tool surface.

Adds an optional httpx_client_factory parameter to:

• RestApiTool.init
• RestApiTool.from_parsed_operation
• OpenAPIToolset.init

OpenAPIToolset forwards the factory to every generated RestApiTool the same way ssl_verify and header_provider are already forwarded. When provided, the factory's client is used to issue each API call; when None (default), the existing httpx.AsyncClient(verify=..., timeout=None) construction is preserved exactly. This unlocks httpx.AsyncClient knobs that the narrower ssl_verify parameter can't reach: proxies, HTTP/2, custom transports (e.g. request signing), and shared connection pools.

Closes #5681

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[rohityan]

Hi @darshil3011 , Thank you for your contribution! We appreciate you taking the time to submit this pull request. Your PR has been received by the team and is currently under review. We will provide feedback as soon as we have an update to share.

[rohityan]

Hi @xuanyang15 , can you please review this.

[darshil3011]

Thanks, looking forward to feedbacks.