optimize find path

[nevermore3]

What type of PR is this?

• bug
• feature
• enhancement

What problem(s) does this PR solve?

Issue(s) number:

Description:

1、Optimize memory usage
2、Simplify the algorithm，please refer to the code comments for details

How do you solve it?

Special notes for your reviewer, ex. impact of this fix, design document, etc:

Checklist:

Tests:

• Unit test(positive and negative cases)
• Function test
• Performance test
• N/A

Affects:

• Documentation affected (Please add the label if documentation needs to be modified.)
• Incompatibility (If it breaks the compatibility, please describe it and add the label.）
• If it's needed to cherry-pick (If cherry-pick to some branches is required, please label the destination version(s).)
• Performance impacted: Consumes more CPU/Memory

Release notes:

Please confirm whether to be reflected in release notes and how to describe:

ex. Fixed the bug .....

[Shylock-Hg]

Do you have benchmark about speed and memory improvement?

[nevermore3]

Do you have benchmark about speed and memory improvement?

the stress test tool does not support Find Path yet,
memory optimization is the previous version saved all paths, now only the path of the previous step is saved

[nevermore3]

refer to #4095