Fix async-std and re-enable Ci for async-std builds

[slawlor]

Resolves #325

[codecov]

Codecov Report

Attention: Patch coverage is 86.00000% with 7 lines in your changes missing coverage. Please review.

Project coverage is 81.61%. Comparing base (a4f92a8) to head (231499d).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
ractor/src/actor/supervision.rs	25.00%	6 Missing ⚠️
ractor/src/actor/tests/supervisor.rs	97.61%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #327      +/-   ##
==========================================
- Coverage   81.61%   81.61%   -0.01%     
==========================================
  Files          61       61              
  Lines       12299    12298       -1     
==========================================
- Hits        10038    10037       -1     
  Misses       2261     2261              

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