Fix probability inaccuracy in reservoir sampling

[chzhoo]

What type of PR is this?

• [x] bug
• [ ] feature
• [ ] enhancement

What problem(s) does this PR solve?

Issue(s) number: 6091

Description:

The <go_statement> SAMPLE <sample_list> statement relay on the reservoir sampling algorithm, but the current implementation exhibits probability inaccuracies.

How do you solve it?

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

Checklist:

Tests:

• [x] 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: Fix probability inaccuracy in reservoir sampling

[CLAassistant]

All committers have signed the CLA.