Rename trainer._launch to trainer._run

[ananthsub]

What does this PR do?

launch might be associated w/ distributed launch or process launch which isn't the case here

cc @carmocca
Fixes #7232 (comment)

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[codecov]

Codecov Report

Merging #7265 (80a2a3c) into master (e272bea) will decrease coverage by 0%.
The diff coverage is 100%.

@@          Coverage Diff           @@
##           master   #7265   +/-   ##
======================================
- Coverage      87%     87%   -0%     
======================================
  Files         199     199           
  Lines       12799   12799           
======================================
- Hits        11170   11168    -2     
- Misses       1629    1631    +2     

[ananthsub]

@tchaton mind taking a look?

[tchaton]

LGTM !