MAINT Add fixture for dataset generation in common tests

[awinml]

Reference Issue

Fixes #672

What does this implement/fix? Explain your changes.

• Created a common fixture to create a sample dataset used in tests.
• Replaced boilerplate code with fixture in necessary tests in estimator_checks.py.

[codecov]

Codecov Report

Patch coverage: 93.33% and project coverage change: -3.25 ⚠️

Comparison is base (8a42dfc) 96.51% compared to head (9f8d6a6) 93.26%.

❗ Current head 9f8d6a6 differs from pull request most recent head 41a726d. Consider uploading reports for the commit 41a726d to get more accurate results

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #932      +/-   ##
==========================================
- Coverage   96.51%   93.26%   -3.25%     
==========================================
  Files         103       94       -9     
  Lines        7280     6204    -1076     
  Branches     1071      666     -405     
==========================================
- Hits         7026     5786    -1240     
- Misses        147      356     +209     
+ Partials      107       62      -45     

Impacted Files	Coverage Δ
imblearn/utils/estimator_checks.py	95.05% <93.33%> (+2.82%)	⬆️

... and 91 files with indirect coverage changes

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[awinml]

@glemaitre Requesting a review. Please can you have a look at the code?

I have added the fixture to create a sample dataset that can be used by all the tests.

[awinml]

The CI fails on unrelated tests. Running the complete test suite locally does not give any errors.

[glemaitre]

A bit late to the party but LGTM. I sync with main. It should be OK now.