access_log: add newline between JSON log lines

[aa-stripe]

Description:
Tack a newline onto the end of all JSON access log lines

Risk Level:
Low

Testing:
Every JSON unit test will now check to see that there is one (and only one) newline in a log line

Docs Changes:
None

Release Notes:
None

Fixes #5018

[aa-stripe]

@htuch @mattklein123 ptal!

[aa-stripe]

Verified manually with this config:

admin:
  access_log_path: /tmp/admin_access.log
  address:
    socket_address: { address: 0.0.0.0, port_value: 9901 }
static_resources:
  listeners:
  - name: listener_0
    address:
      socket_address: { address: 0.0.0.0, port_value: 10000 }
    filter_chains:
    - filters:
      - name: envoy.http_connection_manager
        config:
          access_log:
            name: envoy.file_access_log
            config:
              path: /tmp/envoy.log
              json_format:
                protocol: "%PROTOCOL%"
                duration: "%DURATION%"
                cluster: "%UPSTREAM_CLUSTER%"
                path: "%REQ(X-ENVOY-ORIGINAL-PATH?:PATH)%"
          stat_prefix: ingress_http
          codec_type: AUTO
          route_config:
            name: local_route
            virtual_hosts:
            - name: local_service
              domains: ["*"]
              routes:
              - match: { prefix: "/" }
                route: { host_rewrite: www.google.com, cluster: service_google }
          http_filters:
          - name: envoy.router
  clusters:
  - name: service_google
    connect_timeout: 0.25s
    type: LOGICAL_DNS
    # Comment out the following line to test on v6 networks
    dns_lookup_family: V4_ONLY
    lb_policy: ROUND_ROBIN
    hosts: [{ socket_address: { address: google.com, port_value: 443 }}]
    tls_context: { sni: www.google.com }

[htuch]

Thanks, LGTM just two nits.

[aa-stripe]

@htuch changes made!

[htuch]

Thanks!