SLO Aware Routing Sidecar + Plugin EPP Integration and Helm Deployment

[BenjaminBraunDev]

This PR is stage 3/3 for adding in the latency prediction and SLO-Aware Routing functionality to EPP.

New Features:

1. New -enable-latency-predictor flag in EPP arg to inform it that sidecars are present and to register slo routing plugins.
2. Requests now support latency SLOs in their header (x-slo-ttft-ms and x-slo-tpot-ms) and a boolean for whether to use the SLO routing scheduling profile with slo scoring (x-prediction-based-scheduling). If false, use the default profile and just track and train for future requests.

Plugins

Registers and deploys the plugins added in #1849 via scheduling profiles:

1. The requestcontrol plugins that track requests and their latencies and sends data back to training sidecar for processing.
2. A Scorer plugin based on latencies and headroom.

PodMetrics

Adds (back) the totalRunningRequestsMetric prometheus metric from vLLM, which was removed for being unused in the past, but is now a feature of our latency prediction model.

Guide

Added a guide for how to deploy IGW with SLO-Aware Routing in site-src/guides/slo-aware-routing.md

Fixes #1323

Does this PR introduce a user-facing change?:

Yes:
EPP has a new runtime/deployment argument: `-enable-latency-predictor`

When enabled EPP, will register and support the new SLO routing plugins and sidecars. With this flag, EPP will assume the predictor and training sidecars also exist in its same container.

When latency prediction is enabled for EPP, requests support 3 new headers:
- `x-slo-ttft-ms` is a float for the desired "Time To First Token" SLO
- `x-slo-tpot-ms` is a float for the desired average "Time Per Output Token" SLO
- `x-prediction-based-scheduling` is a boolean for whether to route this request with the default scheduling profile or with the slo-aware scheduling profile

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[k8s-ci-robot]

Hi @BenjaminBraunDev. Thanks for your PR.

I'm waiting for a github.com member to verify that this patch is reasonable to test. If it is, they should reply with /ok-to-test on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work. Regular contributors should join the org to skip this step.

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[ahg-g]

/ok-to-test

[BenjaminBraunDev]

@ahg-g Due to it's large nature, Kellen requested we split this PR up. Here is the first one: #1849

[ahg-g]

it would be great if you can send a separate PR for adding the running requests metric

[ahg-g]

@kaushikmitr @BenjaminBraunDev this is predicted latency, not slo, right? if so, please use predicted-latency-scorer as the name of the plugin.

[BenjaminBraunDev]

Here's the issue regarding the HandleResponseBodyModelStreaming weirdness: #1903

[kfswain]

/approve

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: BenjaminBraunDev, kfswain

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[BenjaminBraunDev]

@kfswain Sorry, forgot to add a small bugfix to the scorer plugin, could you re-approve?

[kfswain]

Np, approval remains. It's the LGTM that's removed. I'll leave that to @kaushikmitr to stamp

[kfswain]

Sry, I wont make you chase down a person again, was just trying to let other people be involved is all.

/lgtm

[BenjaminBraunDev]

Thanks!