Title: dynamic module: new streamable HTTP callout support

Description:

Describe the desired behavior, what scenario it enables and how it
would be used.

The async streamable HTTP client is supported by Envoy in long time ago. With it we can created multiple different HTTP streams to different backends at the same time and distribute requests between these backends.

We can expose the feature to dynamic modules which should make sense for developing of MCP related dynamic modules.

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Any extra documentation required to understand the issue.