FastMRI dataset onboarding script and detailed examples

[ant0nsc]

This PR adds necessary tooling and examples for running fastMRI reconstruction models.

• Script to create and run an Azure Data Factory to download the raw data, and place them into a storage account
• Detailed examples to run the VarNet model from the fastMRI github repo
• Ability to work with fixed mounting points for datasets

[melanibe]

Great new capabilities added 🚀 And really liked the documentation!
Left some minor comments, feel free to ignore if they don't make sense.

[hansenms]

At the moment, the prepare_fastmri.py script does not work. At first glance, there are problems with binary datasets having space in their names, e.g. " On Azure`. I tried a quick hack to remove all the spaces in various names, but I am now getting this error (when running the pipelines):

{"stack":"Error: Error: Error: TypeError: Cannot set property 'enablePartitionDiscovery' of undefined\n    at t.<anonymous> (https://ms-adf.azure.com/main.01ccec2db0cb1598b89b.js:2:1661940)\n    at https://ms-adf.azure.com/polyfills.7135c37b2f707063692f.js:2:112098\n    at Object.throw (https://ms-adf.azure.com/polyfills.7135c37b2f707063692f.js:2:112203)\n    at s (https://ms-adf.azure.com/polyfills.7135c37b2f707063692f.js:2:110993)\n    at e.invoke (https://ms-adf.azure.com/polyfills.7135c37b2f707063692f.js:2:14216)\n    at Object.onInvoke (https://ms-adf.azure.com/main.01ccec2db0cb1598b89b.js:2:3754478)\n    at e.invoke (https://ms-adf.azure.com/polyfills.7135c37b2f707063692f.js:2:14156)\n    at t.run (https://ms-adf.azure.com/polyfills.7135c37b2f707063692f.js:2:9419)\n    at https://ms-adf.azure.com/polyfills.7135c37b2f707063692f.js:2:21175\n    at e.invokeTask (https://ms-adf.azure.com/polyfills.7135c37b2f707063692f.js:2:14900)\n    at Object.onInvokeTask (https://ms-adf.azure.com/main.01ccec2db0cb1598b89b.js:2:3754390)\n    at e.invokeTask (https://ms-adf.azure.com/polyfills.7135c37b2f707063692f.js:2:14821)\n    at t.runTask (https://ms-adf.azure.com/polyfills.7135c37b2f707063692f.js:2:10082)\n    at g (https://ms-adf.azure.com/polyfills.7135c37b2f707063692f.js:2:17167)\n    at t.invokeTask (https://ms-adf.azure.com/polyfills.7135c37b2f707063692f.js:2:16012)\n    at invoke (https://ms-adf.azure.com/polyfills.7135c37b2f707063692f.js:2:15874)\n    at n.args.<computed> (https://ms-adf.azure.com/polyfills.7135c37b2f707063692f.js:2:45244)","message":"Error: Error: TypeError: Cannot set property 'enablePartitionDiscovery' of undefined"}

[hansenms]

correction on my comment above, appears there was an exit(1) in there for debugging purposes that caused the scrip to exit prematurely. Continuing testing with that fixed.

[Shruthi42]

Does this need to be set here? I imagine most containers would override this if necessary (the FastMri container does), and this introduces a small hidden difference between an offline and AzureML run.