Preserve imported statement functions

[awnawab]

An imported statement function (😭 ) with the same root as a target subroutine is overwritten by the dependency transformation. This PR fixes the above.

[github-actions[bot]]

Documentation for this branch can be viewed at https://sites.ecmwf.int/docs/loki/251/index.html

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 92.53%. Comparing base (3fe6ce2) to head (29f41b7).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #251 +/- ## ======================================= Coverage 92.53% 92.53% ======================================= Files 96 96 Lines 17580 17580 ======================================= Hits 16267 16267 Misses 1313 1313 ``` | [Flag](https://app.codecov.io/gh/ecmwf-ifs/loki/pull/251/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=ecmwf-ifs) | Coverage Δ | | |---|---|---| | [lint_rules](https://app.codecov.io/gh/ecmwf-ifs/loki/pull/251/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=ecmwf-ifs) | `96.39% <ø> (ø)` | | | [loki](https://app.codecov.io/gh/ecmwf-ifs/loki/pull/251/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=ecmwf-ifs) | `92.47% <100.00%> (ø)` | | | [transformations](https://app.codecov.io/gh/ecmwf-ifs/loki/pull/251/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=ecmwf-ifs) | `91.98% <ø> (ø)` | | Flags with carried forward coverage won't be shown. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=ecmwf-ifs#carryforward-flags-in-the-pull-request-comment) to find out more.

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