feat(matchers): add AnythingOrNone to match any value including None

[samuelint]

When using decoy.when across multiple test cases, you may want the mock to return a result regardless of the argument values—even if some are None. To handle all combinations, you'd typically need to define multiple matchers like:

decoy.when(
    mock_instance.execute(
        arg1=matchers.Anything(),
        arg2=None,
    )
).then_return(self.some_result)
decoy.when(
    mock_instance.execute(
        arg1=matchers.Anything(),
        arg2=matchers.Anything(),
    )
).then_return(self.some_result)
decoy.when(
    mock_instance.execute(
        arg1=None,
        arg2=matchers.Anything(),
    )
).then_return(self.some_result)

This can be simplified by using a matcher that accepts both None and any value:

decoy.when(
    mock_instance.execute(
        arg1=matchers.AnythingOrNone(),
        arg2=matchers.AnythingOrNone(),
    )
).then_return(self.some_result)

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 98.42%. Comparing base (cb399b7) to head (0d184f9).
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #262      +/-   ##
==========================================
+ Coverage   98.41%   98.42%   +0.01%     
==========================================
  Files          19       19              
  Lines         757      764       +7     
  Branches       93       93              
==========================================
+ Hits          745      752       +7     
  Misses         10       10              
  Partials        2        2              

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