Harmonize extend_frm_*fx() and shrink_frm_*fx()
# Bug description
The function pairs
* `extend_frm_fx()` and `extend_frm_ivas_fx()`
* `shrink_frm_fx()` and `shrink_frm_ivas_fx()`
are almost identical (except from one scaling + `isSilence_ivas_fx()` vs. `isSilence_fx()`) - it should be feasible to harmonize them.
issue