Change traverse implemention to in-order traverse

[qiuchengxuan]

the current traverse implemention has several weakness:

1. unable to stop traverse, thus unable to reduce traverse time complexity around O(logN)
2. out-of-order, ordinary traverse method should be pre-order, in-order, post-order, but the current implemention belongs none of them
3. memory cost, since traversing in flat levels, maximum memory usage will reach to nearly half tree width

[aviary2-wf]

Security Insights

No security relevant content was detected by automated scans.

Action Items

• Review PR for security impact; comment "security review required" if needed or unsure
• Verify aviary.yaml coverage of security relevant code

---

Questions or Comments? Reach out on Slack: #support-infosec.