proxy: wrap QUIC socket with h_11 proxy wrapper (#2593)
proxy: wrap QUIC socket with h_11 proxy wrapper (#2593)

Description: Enable proxy support for requests that go through the `base_h3` cluster. Fixes https://github.com/envoyproxy/envoy-mobile/issues/2556.
Risk Level: Low, guarded with an engine builder feature flag (set with `enableProxying(true/falase)` call.
Testing: Tests
Docs Changes: N/A
Release Notes: N/A

Signed-off-by: Rafal Augustyniak <c112854348d0b65cbb3818b4bb8eb5588417f7f1@lyft.com>
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