SyncProgress was modified in PR #23576 to add the fields reported for
snap sync. The PR also changed ethclient to use the SyncProgress struct
directly instead of wrapping it for hex-decoding. This broke the
SyncProgress method.

Fix it by putting back the custom wrapper. While here, also put back the
fast sync related fields because SyncProgress is stable API and thus
removing fields is not allowed.

Fixes #24180
Fixes #24176