Fix rounding in fiter

[xehartnort]

Implement correct rounding in filter method. Also add a test to ensure perfect rounding. :)

[github-actions]

Coverage Report

File	Stmts	Miss	Cover	Missing
flex/data
dataset.py	122	3	98%	95, 213–214
utils.py	70	15	79%	107–123, 159
flex/datasets
federated_datasets.py	45	13	71%	19, 27–30, 40–55, 73, 86
flexible_datasets.py	11	3	73%	13, 30–31
flex/model
model.py	21	4	81%	30–33
flex/pool
decorators.py	53	2	96%	12–13
primitives.py	50	12	76%	55–65, 195, 236–242
TOTAL	977	52	95%

Tests	Skipped	Failures	Errors	Time
116	0 💤	1 ❌	0 🔥	15m 5s ⏱️

[xehartnort]

Ready to merge!

[AlArgente]

Good name change. It's better to know the number of clients we use when applying the filter instead of working with the number of clients to dropout, can be confusing sometimes.