proxy_protocol: evaluate format_string in upstream added_tlvs (#47369)
Description
This PR fixes the upstream proxy protocol transport socket to honor
format_string in added_tlvs. Before this change only the static
value field was read, so format_string entries were ignored.
These entries are now compiled at config load and evaluated per
connection against the upstream connection stream info, then emitted in
the proxy protocol v2 header. This reuses the same mechanism as the
tcp_proxy filter. An entry that sets both value and format_string,
or neither, is now rejected at config load.
Fix https://github.com/envoyproxy/envoy/issues/45130

Commit Message: proxy_protocol: evaluate format_string in upstream
added_tlvs
Risk Level: Low
Testing: Added Tests
Docs Changes: Added
Release Notes: Added

Signed-off-by: Rohit Agrawal rohit.agrawal@databricks.com
Mirrored from https://github.com/envoyproxy/envoy @ cd73cf5553aa8e03c9d9ce46ca98fcb5b6a45ac9