envoy listener: support tcp keepalive on primary and additional addresses

Commit Message: This change introduces the ability to configure TCP keepalive settings on listener & additional addresses. Currently we have to set the keepalive socket options directly and with this change users can enable TCP keepalive for both primary and additional addresses via the listener configuration similar to the keepalive settings on the clusters.

Additional Description: Configuration example:

static_resources:
  listeners:
  - name: "listener"
    address:
      socket_address:
        address: 127.0.0.1
        port_value: 10000
    # TCP keepalive configuration for the primary address.
    tcp_keepalive:
      keepalive_time: 60000       # time in milliseconds before probing starts
      keepalive_interval: 10000   # interval between probes in milliseconds
      keepalive_probes: 5         # number of abandoned probes before closing connection
    additional_addresses:
      - address:
          socket_address:
            address: 127.0.0.2
            port_value: 10001
        # TCP keepalive override for the additional address.
        tcp_keepalive_override:
          tcp_keepalive
            keepalive_time: 60000
            keepalive_interval: 10000
            keepalive_probes: 5

Risk Level: low Testing: unit and integration Docs Changes: NA Release Notes: NA

Nov 10 '25 12:11 jronak

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

:cat:

Caused by: https://github.com/envoyproxy/envoy/pull/41934 was opened by jronak.

see: more, trace.