Provide the user an option to specify absolute/relative paths for datasets

[NihanthCW]

Describe the bug

This is a follow up to #3414.
As per the discussion, to avoid confusion about the dataset path being absolute or relative, it seems like a better approach to let the users specify how they'd like the dataset path to be saved in the session file.

Impact

• High - User productivity significantly degraded
• Medium - User productivity partially degraded
• Low - User productivity trivially degraded

[shaomeng]

I observe that when I save a session file, there's no question asking me to use relative or absolute path. I'm not sure what's changed.