split experimental_feature flag

[SuperYoko]

What type of PR is this?

• bug
• feature
• enhancement

What problem(s) does this PR solve?

Issue(s) number:

#4729

Description:

experimental flags control toss and data balance at the same time.

How do you solve it?

add 2 sub flag, current config only allow data balance.

# if use experimental features
--enable_experimental_feature=false
# if use toss feature, only work if enable_experimental_feature is true
--enable_toss=false
# if use balance data feature, only work if enable_experimental_feature is true
--enable_data_balance=true

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:

add new flag to support only open toss（not suggest）/ data balance feature

[panda-sheep]

Efficient

[wey-gu]

Thanks!

[wey-gu]

I created the issue before realizing your pr 🙃.

The issue was aligned with @MuYiYong already.

[pengweisong]

Good job.

[jinyingsunny]

cr了代码，没做验证