rename result files from *.mfres.jld2 to *.iesopt.result.jld2

[daschw]

This is still reference to the old MarketFlow name, we should get rid of, right?
Sorry, I did not use conventional commits yet.
Feel free to close if you are already working on this on a local branch.

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 2 lines in your changes missing coverage. Please review.

Project coverage is 36.33%. Comparing base (b98139b) to head (0ef3ea4).
Report is 1 commits behind head on main.

@@           Coverage Diff           @@
##             main       #5   +/-   ##
=======================================
  Coverage   36.33%   36.33%           
=======================================
  Files          93       93           
  Lines        3630     3630           
=======================================
  Hits         1319     1319           
  Misses       2311     2311           

Files	Coverage Δ
src/results/jld2.jl	6.45% <0.00%> (ø)
src/utils/packing.jl	0.00% <0.00%> (ø)

[sstroemer]

Nice, thanks! This also shows that the codecov diff is misconfigured... having +0.00% on the overall project should be fine, and not require 36.33% on the patch (if it changed something that wasn't covered before). I'll merge and will put that into an issue.