refactor: simplify the double echo state change

[hadjiszs]

Description

Simple refactor to ease the split to dedicated tasks

Fixes TP-597

PR Checklist:

• I have performed a self-review of my code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have added or updated tests that comprehensively prove my change is effective or that my feature works

[codecov]

Codecov Report

Merging #254 (f8671fb) into main (21b3d3f) will decrease coverage by 0.06%.
The diff coverage is 93.47%.

❗ Current head f8671fb differs from pull request most recent head 8efdfdc. Consider uploading reports for the commit 8efdfdc to get more accurate results

@@            Coverage Diff             @@
##             main     #254      +/-   ##
==========================================
- Coverage   53.89%   53.83%   -0.06%     
==========================================
  Files         177      177              
  Lines        9264     9248      -16     
==========================================
- Hits         4993     4979      -14     
+ Misses       4271     4269       -2     

Impacted Files	Coverage Δ
crates/topos-tce-broadcast/src/lib.rs	53.70% <ø> (-0.29%)	⬇️
crates/topos-tce-broadcast/src/double_echo/mod.rs	85.50% <93.18%> (-0.21%)	⬇️
crates/topos-tce-broadcast/src/sampler/mod.rs	41.17% <100.00%> (+2.28%)	⬆️
crates/topos-tce-broadcast/src/tests/mod.rs	98.23% <100.00%> (-0.02%)	⬇️