logger: support log control in admin interface and command line option for Fancy Logger (#12369)

Add log control (list and modify log level) in admin interface for Fancy Logger, a new fine-grained logger for Envoy, and provide command line option --enable-fine-grain-logging for developers.

Additional Description: A doc of overview is provided here: source/docs/fancy_logger.md.
Risk Level: Medium
Testing: Unit tests.
Docs Changes: Added a new option --enable-fine-grain-logging and doc it.
Release Notes: Added to current.rst.

Signed-off-by: Jinhui Song <jinhuisong@google.com>

Mirrored from https://github.com/envoyproxy/envoy @ b7138814dde530b8c2957e806ea40879a4fdce32

envoy/admin/v3/server_info.proto

@@ -54,7 +54,7 @@ message ServerInfo {
   CommandLineOptions command_line_options = 6;
 }
 
-// [#next-free-field: 34]
+// [#next-free-field: 35]
 message CommandLineOptions {
   option (udpa.annotations.versioning).previous_message_type =
       "envoy.admin.v2alpha.CommandLineOptions";
@@ -176,4 +176,7 @@ message CommandLineOptions {
 
   // See :option:`--bootstrap-version` for details.
   uint32 bootstrap_version = 29;
+
+  // See :option:`--enable-fine-grain-logging` for details.
+  bool enable_fine_grain_logging = 34;
 }

envoy/admin/v4alpha/server_info.proto

@@ -54,7 +54,7 @@ message ServerInfo {
   CommandLineOptions command_line_options = 6;
 }
 
-// [#next-free-field: 34]
+// [#next-free-field: 35]
 message CommandLineOptions {
   option (udpa.annotations.versioning).previous_message_type = "envoy.admin.v3.CommandLineOptions";
 
@@ -175,4 +175,7 @@ message CommandLineOptions {
 
   // See :option:`--bootstrap-version` for details.
   uint32 bootstrap_version = 29;
+
+  // See :option:`--enable-fine-grain-logging` for details.
+  bool enable_fine_grain_logging = 34;
 }