Add a tutorial demonstrating 2D image restoration using the MONAI Restormer model. (#1987)

### Add a tutorial demonstrating 2D image restoration using the MONAI
Restormer model.

Fixes: Completes issue from main MONAI repo: [#8261](
Project-MONAI/MONAI#8261)
None 

### Description
This notebook covers setting up the environment, loading data,
initializing a small Restormer model configuration, training a
small-scale demonstrative example with the Restorme,r and visualizing
the restoration results on noisy images.

### Checks
<!--- Put an `x` in all the boxes that apply, and remove the not
applicable items -->
- [x] Avoid including large-size files in the PR.
- [x] Clean up long text outputs from code cells in the notebook.
- [x] For security purposes, please check the contents and remove any
sensitive info such as user names and private key.
- [x] Ensure (1) hyperlinks and markdown anchors are working (2) use
relative paths for tutorial repo files (3) put figure and graphs in the
`./figure` folder
- [x] Notebook runs automatically `./runner.sh -t <path to .ipynb file>`

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Signed-off-by: Cano-Muniz, Santiago <[email protected]>
Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Co-authored-by: Eric Kerfoot <[email protected]>

Author: 3 people