use PyWavelet for CWT

[igor-pechersky]

#1096

[nils-braun]

Thank you very much for taking the time to do the fix! I am ok with the changes. Did you have a chance to check the resulting features, are they the same?

Could you also fix the styling issue in the code? Thanks!

[nils-braun]

I have seen in the CI/CD that the pywavelets package in the version you were using is not available for python versions 3.9 and older. I can (and should!) drop the python versions 3.7 and 3.8, but 3.9 has not reached end of life yet, so I would like to keep it.
I see two options here:

• the code implements two branches for versions that support this pywavelets and one that does not
• we limit the scipy version (not favoured, but if there is no other way...)

Is this particular version of pywavelets needed?

Update: I did remove python 3.7 an 3.8 from the CI/CD an added 3.10-3.12. I added a limit for scipy to make the CI/CD succeed for now.