access_log: add UNIQUE_ID substitution string (#34817)

Commit Message: Add UNIQUE_ID substitution string in the access log.
Additional Description: Envoy access log today doesn't have the concept
of unique log id which is guaranteed to be always present always when
emitting an access log record. This will ensure every access log record
when uses % UNIQUE_ID% in schema gets a UUID.
Risk Level: Low
Testing: Unit test has been added to ensure the UNIQUE_ID provides
unique value for every invocation of parse. Local testing has also been
performed to ensure the UNIQUE_ID is emitted from all filter levels
(example - listener filter access log, http connection manager access
log, tcp_proxy access log) for good and bad requests (which are
malformed and expected to fail at http parser level).
Docs Changes: Updated Access log documentation to provide the new
UNIQUE_ID support.
Release Notes: N/A
Platform Specific Features: N/A
[Optional Runtime guard:]
[Optional Fixes #Issue]
[Optional Fixes commit #PR or SHA]
[Optional Deprecated:]
[Optional [API
Considerations](https://github.com/envoyproxy/envoy/blob/main/api/review_checklist.md):]

---------

Signed-off-by: Chaitra Reddy Vontela <cvontela@microsoft.com>
Co-authored-by: Chaitra Reddy Vontela <cvontela@microsoft.com>

Mirrored from https://github.com/envoyproxy/envoy @ 6cb0b30d6be9302025e09248a4327bac7a7e8cf1

envoy/config/cluster/v3/cluster.proto

@@ -754,13 +754,13 @@ message Cluster {
 
   reserved "hosts", "tls_context", "extension_protocol_options";
 
-  // Configuration to use different transport sockets for different endpoints.  The entry of
+  // Configuration to use different transport sockets for different endpoints. The entry of
   // ``envoy.transport_socket_match`` in the :ref:`LbEndpoint.Metadata
   // <envoy_v3_api_field_config.endpoint.v3.LbEndpoint.metadata>` is used to match against the
   // transport sockets as they appear in the list. If a match is not found, the search continues in
   // :ref:`LocalityLbEndpoints.Metadata
-  // <envoy_v3_api_field_config.endpoint.v3.LocalityLbEndpoints.metadata>`.  The first :ref:`match
-  // <envoy_v3_api_msg_config.cluster.v3.Cluster.TransportSocketMatch>` is used.  For example, with
+  // <envoy_v3_api_field_config.endpoint.v3.LocalityLbEndpoints.metadata>`. The first :ref:`match
+  // <envoy_v3_api_msg_config.cluster.v3.Cluster.TransportSocketMatch>` is used. For example, with
   // the following match
   //
   // .. code-block:: yaml