Add adjusted eval command to allow switching the file while rendering

[lorenzboguhn]

This PR aims to make the plug-in more user friendly.
This will adjust the file that will be rendered to the current open file.
This allows to quickly change the file you are working currently while having the output of the current open file.
This is way more interactive than always closing the old evaluation window and restart the evaluation (by using a shortcut or command palette interaction).

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[lorenzboguhn]

Hi @julienduchesne, thanks for merging the other PR.
Would you mind to take a look on this PR ?
Again, I am willing to further improve this PR if needed, if there is any further feedback.