server: add a CLI option to disable extensions (#9125)

*Description:*

Add a new `--disable-extensions` flag that hides the named extensions
from their corresponding factory registry. The extensions are retained
in the registry factory, but the factory pointer is nulled so that
configuration attempts to use the extensions will fail.

*Risk Level:* Medium
*Testing:* Added unit tests, manual verification.
*Docs Changes:* Added to CLI reference.
*Release Notes:* Added release note.
*Fixes:* #9096

Signed-off-by: James Peach <jpeach@apache.org>

Mirrored from https://github.com/envoyproxy/envoy @ 445d0ee4a64738f1de072537fb364d9096478915

envoy/admin/v2alpha/server_info.proto

@@ -47,7 +47,7 @@ message ServerInfo {
   CommandLineOptions command_line_options = 6;
 }
 
-// [#next-free-field: 28]
+// [#next-free-field: 29]
 message CommandLineOptions {
   enum IpVersion {
     v4 = 0;
@@ -143,4 +143,7 @@ message CommandLineOptions {
 
   // See :option:`--cpuset-threads` for details.
   bool cpuset_threads = 25;
+
+  // See :option:`--disable-extensions` for details.
+  repeated string disabled_extensions = 28;
 }

envoy/admin/v3alpha/server_info.proto

@@ -51,7 +51,7 @@ message ServerInfo {
   CommandLineOptions command_line_options = 6;
 }
 
-// [#next-free-field: 28]
+// [#next-free-field: 29]
 message CommandLineOptions {
   option (udpa.annotations.versioning).previous_message_type =
       "envoy.admin.v2alpha.CommandLineOptions";
@@ -147,4 +147,7 @@ message CommandLineOptions {
 
   // See :option:`--cpuset-threads` for details.
   bool cpuset_threads = 25;
+
+  // See :option:`--disable-extensions` for details.
+  repeated string disabled_extensions = 28;
 }