Short expansion of conditional mutual information

[kahaaga]

No need for review here yet. I still have some polishing to do.

Implements #309

What is in this PR?

• New conditional association measure ShortExpansionConditionalMutualInformation (SECMI for short).
• New independence test SECMITest based on this measure.
• Examples.
• Tests.

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 93.75000% with 4 lines in your changes missing coverage. Please review.

Project coverage is 94.91%. Comparing base (27a2bb8) to head (6ad1ed5).

Files	Patch %	Lines
.../short_expansion_conditional_mutual_information.jl	88.00%	3 Missing ⚠️
src/independence_tests/secmi/secmi_test.jl	96.87%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #387      +/-   ##
==========================================
- Coverage   94.94%   94.91%   -0.03%     
==========================================
  Files         111      113       +2     
  Lines        3205     3265      +60     
==========================================
+ Hits         3043     3099      +56     
- Misses        162      166       +4     

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