Local reply is not forwarding `x-request-id` header to ext-proc

[xr]

Description:
Supposed we have a filter chain:

request -> jwt_authn -> ext-proc -> upstream

when jwt_authn failed it will trigger local reply, ext-proc will get from the OnResponseHeaders phases onwards, however, the request to ext-proc only contain a small set of the request headers, for example:

headers:{headers:{key:":status" raw_value:"401"} headers:{key:"www-authenticate" raw_value:"Bearer realm=\"http://localhost:10000/api\", error=\"invalid_token\""} headers:{key:"content-length" raw_value:"28"} headers:{key:"content-type" raw_value:"text/plain"}}

my question is:
is there any way to allow local reply to carry more headers? like x-request-id, so that ext-proc could do some processing based on the x-request-id, since it will hit the ext-proc filter anyway (onResponseHeaders)

notes

1. i have configured HCM to generate requestId and preserve in response
2. potentially we could use local reply modification to modify the response, but it would be great if ext_proc could capture those headers anyway. As the local reply modification has less flexibilities, for example, can not only modify certain field inside the response body

[alyssawilk]

cc @gbrail @stevenzzzz @tyxia @mattklein123 @yanavlasov @yanjunxiang-google