Merge "[Thread] add error code ERROR_UNKNOWN for forward compatibility" into main am: 649571ddf7 am: 9750fc3518

Original change: https://android-review.googlesource.com/c/platform/packages/modules/Connectivity/+/2910724

Change-Id: Iac6cc47a412bcbe6ea58cbb3880c094870eb3daa
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>