Add CommitIdentity Function to the CertificateStore

This function will be used to commit a certificate with a key that
exists in the temporary storage location, while moving the temporary
identity to the permanent location in one DB update.

Change-Id: I8b731986073d72d9b6d3b36ee7f2fcfc80b67633
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5269744
Auto-Submit: Sébastien Lalancette <seblalancette@chromium.org>
Reviewed-by: Hamda Mare <hmare@google.com>
Commit-Queue: Sébastien Lalancette <seblalancette@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1256808}