Merge branch 'ns/core-fsyncmethod' into ps/fsync-refs

* ns/core-fsyncmethod: core.fsync: documentation and user-friendly aggregate options core.fsync: new option to harden the index core.fsync: add configuration parsing core.fsync: introduce granular fsync control infrastructure core.fsyncmethod: add writeout-only mode wrapper: make inclusion of Windows csprng header tightly scoped