WIP: lb: PeakEWMA load balancer

[jizhuozhi]

Commit Message: PeakEWMA load balancer
Additional Description:
An improved PeakEWMA load balancer implementation, using P2C(Power of 2 Choices) with weighted active request and error rate fixed latency. The score of a host can be expressed by the following formula (the lower, the better)

$$ Score = \frac{active\_req + 1}{weight} * \frac{decay\_rtt}{1 - \frac{decay\_err}{decay\_total + 1}} $$

Risk Level: Medium
Testing:
Docs Changes:
Release Notes:
Platform Specific Features:
[Optional Runtime guard:]
[Optional Fixes #Issue]
#20907
[Optional Fixes commit #PR or SHA]
[Optional Deprecated:]
[Optional API Considerations:]

[repokitteh-read-only]

Hi @jizhuozhi, welcome and thank you for your contribution.

We will try to review your Pull Request as quickly as possible.

In the meantime, please take a look at the contribution guidelines if you have not done so already.

🐱

Caused by: #32942 was opened by jizhuozhi.

see: more, trace.

[htuch]

@tonya11en assigning your way for review as SME.

[tonya11en]

I'll happily take a look once it's ready for review.

/wait

[github-actions]

This pull request has been automatically marked as stale because it has not had activity in the last 30 days. It will be closed in 7 days if no further activity occurs. Please feel free to give a status update now, ping for review, or re-open when it's ready. Thank you for your contributions!

[github-actions]

This pull request has been automatically closed because it has not had activity in the last 37 days. Please feel free to give a status update now, ping for review, or re-open when it's ready. Thank you for your contributions!