Fix case when init or update NestedMapping with another NestedMapping

[teutoburg]

This caused weird warnings in ScopeSim, because the update method would get the bang-keys from the NestedMapping instance used to init another one. What we probably really want in that case anyway is to init (or update) it with the internal nested dict of the NestedMapping. This should fix those warnings.

Edit: Apparently this is still triggered in mocks (patch dict) within testing (I think the mock patch used .update() with all keys to restore the original dict). So downgrading to DEBUG and changing wording, because this is then normal, but still shouldn't happen outside mocking.

[codecov]

Codecov Report

Attention: 1 lines in your changes are missing coverage. Please review.

Comparison is base (73babb4) 99.36% compared to head (e13230f) 99.04%.
Report is 1 commits behind head on main.

Files	Patch %	Lines
astar_utils/nested_mapping.py	66.66%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #31      +/-   ##
==========================================
- Coverage   99.36%   99.04%   -0.32%     
==========================================
  Files           5        5              
  Lines         313      315       +2     
==========================================
+ Hits          311      312       +1     
- Misses          2        3       +1     

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