[MRG] Add tests about type and GPU for emd/emd2 + 1d variants + wasserstein1d

[rflamary]

Types of changes

• Docs change / refactoring / dependency upgrade
• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Motivation and context / Related issue

How has this been tested (if it applies)

Checklist

• The documentation is up-to-date with the changes I made.
• I have read the CONTRIBUTING document.
• All tests passed, and additional code has been covered with new tests.

[codecov]

Codecov Report

Merging #304 (ead6527) into master (2fe69eb) will increase coverage by 0.01%.
The diff coverage is 85.71%.

@@            Coverage Diff             @@
##           master     #304      +/-   ##
==========================================
+ Coverage   93.41%   93.43%   +0.01%     
==========================================
  Files          21       21              
  Lines        4848     4860      +12     
==========================================
+ Hits         4529     4541      +12     
  Misses        319      319