Leftover #TODO from in `impact.py` merged from `Feature/refractor_impact_calc` branch

[manniepmkam]

In the impact.py script, there are 4 #TODO flags in line 206, 315, 397 and 1122. They are merged from the Feature/refractor_impact_calc branch. This issue is a reminder to update the method, or remove the #TODO if the updates have been done.

[peanutfun]

To sort this a bit, the TODOs are

• L206: Rename from_eih
• L315: Rewrite and deprecate calc_risk_transfer
• L397: Rewrite and deprecate local_exceedance_imp
• L1122: Rewrite and deprecate _loc_return_imp

It is not clear to my why any of these need to be "rewritten and deprecated"

[chahank]

I am the one that wrote these To Do.

• Rename from_eih: it was discussed at the time of the review that this name is a bit cryptic, but no better name was found during the review.
• Rewrite and deprecate calc_risk_transfer : This method is abusing a bit the object-oriented logic of Python. It also only serves currently limited internal purposes, and it's functionality was already re-written in the methods transfer_risk and residual_risk. Now, one simply needs to "clean-up".
• Rewrite and deprecate local_exceedance_imp and _loc_return_imp: These methods have several issues, among others performance, style, and meaning. C.f. issue Negative TC impacts: a question about how we calculate exceedences for centroids #209