Upgrade upload-artifact and download-artifact actions to version 4

[shraddha]

Currently we are using version 3 for upload-artifact and download-artifact actions.
We need to upgrade it to version 4 for better compatibility and improving performance optimizations during uploading and downloading in a faster and efficient way.

[shraddha]

We have tried to do this a few months back. But we had to change it back to version 3
Reference - cdc3bd0

The reason for this downgrade was - If an experiment contained more number of files and if they are uploaded parallelly, it stopped working causing more problems.

So, during this upgrading we should make sure the parallel uploading (or downloading) of files should be handled well.