History attribute shows args as kwargs

[aulemahal]

Pull Request Checklist:

• This PR addresses an already opened issue (for bug fixes / features)
  • This PR fixes update_xclim_history misreporting keyword arguments #963
• Tests for the changes have been added (for bug fixes / features)
• Documentation has been added / updated (for bug fixes / features)
• HISTORY.rst has been updated (with summary of main changes)
  • Link to issue (:issue:number) and pull request (:pull:number) has been added.
• bumpversion patch has been called on this branch
• The relevant author information has been added to .zenodo.json

What kind of change does this PR introduce?

• The "history" attribute added by xclim will was changed:
  • The trailing dot was dropped.
  • None inputs are now printed as "None" (and not "<NoneType>").
  • Arguments are always printed as keyword-arguments. This mostly impacts sdba functions, as it was already the case for Indicators.

Example:

from xclim.core.formatting import update_xclim_history
from xclim.testing import open_dataset

@update_xclim_history
def func(da, arg1, arg2=None, arg3=None):
    return da

ds = open_dataset('ERA5/daily_surface_cancities_1990-1993.nc')
out = func(ds.tas, 1, arg2=[2, 2], arg3=None)

print(out.attrs['history'])

Before: [2021-12-20 10:38:35] tas: func(tas, 1, <list>, <NoneType>) - xclim version: 0.32.1.
Now: [2022-02-16 14:58:50] tas: func(da=tas, arg1=1, arg2=<list>, arg3=None) - xclim version: 0.33.2

Does this PR introduce a breaking change?

I guess that it does, if anyone was parsing that string.

[coveralls]

Coverage increased (+0.009%) to 91.547% when pulling f368b31 on fix-963 into f03d862 on master.