chore: update crates structure for api/uci and core

[Freyskeyd]

Description

Update the structure of the crates topos-core topos-uci and topos-api in order to group them.

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

[gruberb]

👍 LGTM!

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (4aa6a9e) 66.79% compared to head (e3b3c10) 68.03%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #436      +/-   ##
==========================================
+ Coverage   66.79%   68.03%   +1.24%     
==========================================
  Files         220      224       +4     
  Lines       12099    13110    +1011     
==========================================
+ Hits         8082     8920     +838     
- Misses       4017     4190     +173     

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