dfp: add support for DFP honoring dynamic_host filter state when configured

[agrawroh]

Description

The HTTP Dynamic Forward Proxy filter doesn't honor the envoy.upstream.dynamic_host filter state value that's set in the stream info, while both the SNI Dynamic Forward Proxy and UDP Dynamic Forward Proxy filters properly check for and use this value.

This inconsistency means host overriding via filter state works for SNI/UDP proxies but not for HTTP proxies. IMO the behavior is a bit confusing when trying to use the same filter state mechanism across different proxy types.

Changes

This PR adds a new flag called allow_dynamic_host_from_filter_state which when enabled allows HTTP DFP filter to use the filter state values for host and port lookups.

Fixes: #39579

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Commit Message: dfp: add support for DFP honoring dynamic_host filter state when configured
Additional Description: Add support for DFP to honor dynamic_host and dynamic_port filter state values when configured.
Risk Level: Low
Testing: Added Unit & Integration Tests
Docs Changes: Added
Release Notes: Added

[repokitteh-read-only]

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🐱

Caused by: #39605 was opened by agrawroh.

see: more, trace.

[repokitteh-read-only]

CC @envoyproxy/api-shepherds: Your approval is needed for changes made to (api/envoy/|docs/root/api-docs/).
envoyproxy/api-shepherds assignee is @adisuissa
CC @envoyproxy/api-watchers: FYI only for changes made to (api/envoy/|docs/root/api-docs/).

🐱

Caused by: #39605 was opened by agrawroh.

see: more, trace.