Adopt Async Shutdown

[0xTim]

These changes are now available in 2.10.0

Fixes an issue where Fluent Postgres would hang, especially when installing the NIO Event Loop executor.

Drops support for Swift 5.8

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 63.39%. Comparing base (e2988a8) to head (8164723).
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #221      +/-   ##
==========================================
- Coverage   63.77%   63.39%   -0.38%     
==========================================
  Files           8        8              
  Lines         334      336       +2     
==========================================
  Hits          213      213              
- Misses        121      123       +2     

Files with missing lines	Coverage Δ
...es/FluentPostgresDriver/FluentPostgresDriver.swift	86.66% <100.00%> (-13.34%)	⬇️
.../FluentPostgresDriver/PostgresError+Database.swift	92.30% <ø> (ø)