Optimize welcome doc (#8030)

* Removed Download section and added CTA

* Updated use cases
- Removed mult table transaction
- Expanded ML Reproducibility
- Shorten Rollback

* Add files via upload

Uploaded New integration doc and excalidraw

* Updated reference to new images

* Add files via upload

Updated the image fixing a typo

* removed extra section

* Delete old what_is.png image

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Co-authored-by: Your Name <[email protected]>