Chat Completion: common model sorting and grouping settings, improved NanoGPT model list (#5536)

* Improve NanoGPT Model List

* Update token multiplier condition to !== 1 to support showing discounts

* Add Model Sorting

* rework sorting to be more compact

* feat: combine CC model sorting/grouping settings

Co-authored-by: Copilot <copilot@github.com>

* fix: adjust migration logic

Co-authored-by: Copilot <copilot@github.com>

* feat: implement grouping for Chutes

* fix: apply review suggestions

* fix: call reconnect instead of direct status check

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Co-authored-by: Cohee <18619528+Cohee1207@users.noreply.github.com>
Co-authored-by: Copilot <copilot@github.com>