Add downstreamRemoteAddress() method to Lua filter stream info object API

[kenjenkins]

Title: Add downstreamRemoteAddress() method to Lua filter stream info object API

Description:
The Lua filter stream info object API currently provides access to the local address and the downstream direct remote address, but not the downstream remote address. (The main difference being that the "downstream remote address" takes into account the xff_num_trusted_hops setting, while the "downstream direct remote address" does not.)

Could we add a downstreamRemoteAddress() method to this API?

Relevant Links:

The downstreamDirectRemoteAddress() API method appears to have been added in #13536.

Documentation reference for the current Lua filter stream info object API: https://www.envoyproxy.io/docs/envoy/latest/configuration/http/http_filters/lua_filter#stream-info-object-api