Fix issue with image output from Jupyter kernels that didn't use base64 padding (#20561)

This upgrades `nbformat` and `runtimelib` to handle jupyter types with
even more validation and flexiblity. This also processes any multiline
string data coming from the kernel, including with image data (like
`image/png`). While I was at it I also fixed a longstanding issue around
images by eliminating all whitespace (something `atob` does) and using
the no pad decoder.

Fixes: #17956

Before:

<img width="741" alt="image"
src="https://github.com/user-attachments/assets/37ec2cae-ce78-4475-aaa3-4d785e4015d0">

After:

<img width="727" alt="image"
src="https://github.com/user-attachments/assets/e2431ba2-048b-4205-9898-54f357795a9c">


Release Notes:

- Fixed issue with image output from REPL kernels that didn't use base64
padding