Remove id variable from XGI

[nwlandry]

This fixes #619. Note that this breaks the API, because now the add_edge method accepts the idx parameter, and not the id parameter.

[codecov]

Codecov Report

Attention: Patch coverage is 95.45455% with 8 lines in your changes missing coverage. Please review.

Project coverage is 93.42%. Comparing base (8a6bac9) to head (ab5364c).
Report is 2 commits behind head on main.

Files with missing lines	Patch %	Lines
xgi/drawing/draw.py	0.00%	5 Missing ⚠️
xgi/core/simplicialcomplex.py	94.00%	3 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #620   +/-   ##
=======================================
  Coverage   93.42%   93.42%           
=======================================
  Files          63       63           
  Lines        4912     4912           
=======================================
  Hits         4589     4589           
  Misses        323      323           

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

---

🚨 Try these New Features:

• Flaky Tests Detection - Detect and resolve failed and flaky tests

[review-notebook-app]

Check out this pull request on 

See visual diffs & provide feedback on Jupyter Notebooks.

---

Powered by ReviewNB

[maximelucas]

Small comment, rest looks good to me.