[unstable option] `imports_granularity`

[karyon]

Tracking issue for unstable option: imports_granularity.

See Processes.md, "Stabilising an Option":

• Is the default value correct?
• The design and implementation of the option are sound and clean.
• The option is well tested, both in unit tests and, optimally, in real usage.
• There is no open bug about the option that prevents its use.

[calebcartwright]

Thanks but closing as a duplicate of #4991