Revert "[ENSCORESW-922]. Problem with circular chromosomes when feature start/end wrt slice are negative."
There's still a problem when min_start turns out to be greater than max_end.
Need to figure out how to cope with this case.
This reverts commit 72b4782f1fd33692afa3ea4e312b27f25aea19bb.
Revert "[ENSCORESW-922]. Can use the same code fragment for both circular/non-circular chromosomes."

This reverts commit a90ea06d6b0cfd8b41526977d42ce95bd3a2a7c1.
[ENSCORESW-922]. Problem with circular chromosomes when feature start/end wrt slice are negative.
The computation of min_start/max_end is not reliable in this case, so I've added an extra condition
testing whether the relateive coordinates are positive.
When there are negative coordinates, the recomputed slice boundaries will not represent the exact
extent of the region spanned by the transcript, but this shouldn't be a problem so all transcript
IDs are included in the following fetch_all_by_Slice query.
[ENSCORESW-922]. Correct condition for features with negative slice relative coordinates.
[ENSCORESW-922]. Correct condition for features with negative slice relative coordinates.
[ENSCORESW-922]. Correct condition for features with negative slice relative coordinates.
[ENSCORESW-922]. Correct condition for features with negative slice relative coordinates.