feat: remove async_timeout dependency

[bdraco]

One of the goals here is no required deps. While async_timeout is light, we can get rid of it

[codecov]

Codecov Report

Patch coverage: 75.00% and project coverage change: -0.33% ⚠️

Comparison is base (04d6451) 82.83% compared to head (c0db9db) 82.51%.
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #218      +/-   ##
==========================================
- Coverage   82.83%   82.51%   -0.33%     
==========================================
  Files          27       27              
  Lines        3222     3220       -2     
  Branches      669      668       -1     
==========================================
- Hits         2669     2657      -12     
- Misses        339      345       +6     
- Partials      214      218       +4     

Files Changed	Coverage Δ
src/dbus_fast/__version__.py	0.00% <0.00%> (ø)
src/dbus_fast/aio/message_bus.py	85.57% <100.00%> (-0.14%)	⬇️

... and 2 files with indirect coverage changes

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