misc: add init to xdsl frontend

[superlopuh]

Now this is just weird, because we were supposed to have ruff catch this, but there you go.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 90.15%. Comparing base (02941a6) to head (c35e062).
Report is 2 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #3975   +/-   ##
=======================================
  Coverage   90.15%   90.15%           
=======================================
  Files         458      458           
  Lines       58284    58284           
  Branches     5690     5690           
=======================================
  Hits        52547    52547           
  Misses       4346     4346           
  Partials     1391     1391           

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