Implement ratio_max scaling for downsamplers

[MaxiBoether]

Before, we only were able to enter ratios from 0-100 as percentages for downsamplers. With this PR, we allow scaling by a ratio_max factor.

[github-actions]

^{( % to main)
( % to main)}

[codecov]

Codecov Report

Attention: Patch coverage is 93.93939% with 2 lines in your changes missing coverage. Please review.

Project coverage is 82.30%. Comparing base (70e2a57) to head (9a51476).

Files	Patch %	Lines
modyn/config/schema/pipeline/config.py	93.33%	1 Missing ⚠️
...ig/schema/pipeline/sampling/downsampling_config.py	83.33%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #541      +/-   ##
==========================================
+ Coverage   82.29%   82.30%   +0.01%     
==========================================
  Files         217      217              
  Lines       10097    10118      +21     
==========================================
+ Hits         8309     8328      +19     
- Misses       1788     1790       +2     

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[XianzheMa]

LGTM