Reland "OTel: register the create custom service endpoint"

This reverts commit 86d5523c094845a45eb9127871084d55cbab1b82.

Revert submission 151814-revert-151589-TOYEQNWXAI

Reason for revert: Fix failing tests

Reverted changes: /q/submissionid:151814-revert-151589-TOYEQNWXAI

Change-Id: I5a8f498126ee68081e4784f065ea2b9286fbf2a6