[MRG] numItermax in 64 bits in EMD solver

[ncassereau]

List of changes

• Allow test_mm_convergence in test_unbalanced.py to run with Cupy (which does not allow implicit conversion)
• Make numIter a 64bits variable in the Cython code
• Add it to RELEASES.md

Motivation and context / Related issue

When the OpenMP version of EMD was added, the computation of the plan was converted to 64 bits. However, one variable was forgotten, which is the max number of iterations. In the C code, it is a size_t variable, hence usually 64 bits, but the Cython link between C and Python uses an int to store the value. I intend to make it 64 bits as well to allow high numbers of iterations.

How has this been tested (if it applies)

I run all tests on Jean Zay.

PR checklist

• I have read the CONTRIBUTING document.
• The documentation is up-to-date with the changes I made (check build artifacts).
• All tests passed, and additional code has been covered with new tests.
• I have added the PR and Issue fix to the RELEASES.md file.

[codecov]

Codecov Report

Merging #380 (467505c) into master (951209a) will decrease coverage by 0.03%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master     #380      +/-   ##
==========================================
- Coverage   93.79%   93.76%   -0.04%     
==========================================
  Files          23       23              
  Lines        5934     5934              
==========================================
- Hits         5566     5564       -2     
- Misses        368      370       +2