Move migrations in sub-directories

[martinboulais]

I DON'T have JIRA ticket

• [X] explain what this PR does
• [X] if it is a new feature, explain how you plan to use it
• [X] tests are added
• [X] documentation was updated or added

Notable changes for developers:

• Migrations are now grouped by release to have less files in one directory

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 44.28%. Comparing base (c923f23) to head (1ba606e). Report is 104 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1758      +/-   ##
==========================================
+ Coverage   43.38%   44.28%   +0.89%     
==========================================
  Files         882      982     +100     
  Lines       15497    16242     +745     
  Branches     2895     2901       +6     
==========================================
+ Hits         6724     7192     +468     
- Misses       8773     9050     +277     

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[martinboulais]

Dupplicate of https://github.com/AliceO2Group/Bookkeeping/pull/1857