Restore GAMSModel.__init__(…, name_=…) argument

[khaeru]

Removal of this argument in #581 broke message_ix and message-ix-models main branches, as evidenced by scheduled CI, for instance here:

FAILED message_ix/tests/util/test_gams_io.py::test_add_default_data_to_container_data_list[ixmp4] - TypeError: GAMSModel.__init__() takes 1 positional argument but 2 were given
= 220 failed, 41 passed, 5 xfailed, 1 xpassed, 4 warnings, 114 errors in 60.77s (0:01:00) =

Related:

• Remove types.GamsModelInitKwargs.name_.
• Use GamsModelInitKwargs for GAMSModel only. Other functions, like ixmp.model.get_model() and Scenario.solve(), must be usable with any subclass of ixmp.model.base.Model. If such subclasses are created in the future (see for instance Migrating away from GAMS message_ix#879 (comment)) they may have different arguments than GAMSModel.

Also:

• Reduce log verbosity in .base.Model.initialize_items(). Changes to this method in Enable strict mypy settings #581 resulted in spurious messages like:

  Existing index names of 'renewable_potential' ('node', 'commodity', 'grade', 'level', 'year') do not match ()
  

  These are spurious because an argument value of idx_names=() used when creating a parameter is automatically replaced with the same value as idx_sets, resulting in the values shown; so there is no difference.

How to review

• Read the diff and note that the CI checks all pass.
• Run the message_ix test suite with the code on this branch.

PR checklist

• Continuous integration checks all ✅
• Add or expand tests; coverage checks both ✅
• Add, expand, or update documentation. Bugfix.
• Update release notes.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 98.1%. Comparing base (dc208c8) to head (f0e0897).
⚠️ Report is 24 commits behind head on main.

Additional details and impacted files

@@          Coverage Diff          @@
##            main    #587   +/-   ##
=====================================
  Coverage   98.0%   98.1%           
=====================================
  Files         51      51           
  Lines       6260    6262    +2     
=====================================
+ Hits        6141    6145    +4     
+ Misses       119     117    -2     

Files with missing lines	Coverage Δ
ixmp/core/scenario.py	99.2% <ø> (ø)
ixmp/model/__init__.py	100.0% <100.0%> (ø)
ixmp/model/base.py	100.0% <100.0%> (ø)
ixmp/model/gams.py	100.0% <100.0%> (ø)
ixmp/tests/test_model.py	100.0% <100.0%> (ø)

... and 1 file with indirect coverage changes

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