The tracker never influenced traversal: walkdir's follow behavior is
fixed up front by follow_links(), and should_follow() only gated the
tracker's own bookkeeping. Its 'depth limit' compared tree depth (not
symlink chain depth), so RUSTFS_CAPACITY_MAX_SYMLINK_DEPTH was a
complete no-op while its telemetry claimed symlinks were skipped that
walkdir had in fact followed and counted; record_symlink was always
called with size 0, so tracked_bytes never left zero (S12).
Remove the tracker, its skipped/summary events, the symlink metric and
the depth env knob end to end (the env's 'as u8' truncation goes with
it), and document the real semantics at the walker: follow_links(true)
counts targets with walkdir's ancestor-loop detection breaking cycles,
follow_links(false) — the default — counts no symlink targets. The scan
root itself is pre-resolved since backlog#1015.
Ref: rustfs/backlog#1018 (S12 from audit rustfs/backlog#1010)