1990 handle imported variable in kernel extraction

[hiker]

Fixes #1990

[arporter]

Almost there now. Main thing is to check what Stylist actually checks in LFRic and use this information in a comment to justify the removal of 'private/protected' clauses. Apart from that there are some minor things to tidy. Updated User Guide builds fine, as does Reference Guide.
Examples are all fine with compilation enabled (although this is checked by the integration tests anyway).

[hiker]

My apologies for first discussing the need to remove private/protected - given the progress I've made with FAB, I've decided to just not include this anymore, so I hope a major concern for you is gone :) I've also updated the documentation correspondingly.

I am triggering CI now, then it should be ready for next review.

[arporter]

All looks good now, thanks Joerg.
I've brought the branch up to master and I've fired off those integration tests that currently work (i.e. not LFRic unfortunately).
If that's all fine then this is ready to go.

[arporter]

Integration tests were green.