Bugfix: Fix file sync with NFD/NFC filename normalization differences on macOS

After a migration from 6.x to 7.x, files whose names were stored in
NFD form locally but NFC form on the server were incorrectly treated as
a delete and re-upload instead of a rename. Local normalization-only
renames are now detected and not propagated to the server, since these
differences are not visible to users.

https://github.com/owncloud/client/pull/12336
https://github.com/owncloud/client/pull/12356
