Revise async commands support

[gwynne]

These changes are now available in 4.14.0

Changes:

• Deprecates unnecessary API
• Corrects the sync Command adapter methods
• Cleans up some concurrency warnings

[codecov-commenter]

Codecov Report

Merging #196 (104578c) into main (18262d2) will increase coverage by 0.04%.
The diff coverage is 33.33%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #196      +/-   ##
==========================================
+ Coverage   48.25%   48.30%   +0.04%     
==========================================
  Files          44       45       +1     
  Lines        1892     1884       -8     
==========================================
- Hits          913      910       -3     
+ Misses        979      974       -5     

Files	Coverage Δ
...s/ConsoleKitCommands/Async/AsyncCommandGroup.swift	90.56% <ø> (+11.87%)	⬆️
...onsoleKitTerminal/Activity/ActivityIndicator.swift	68.00% <ø> (ø)
...urces/ConsoleKitTerminal/Output/Console+Wait.swift	100.00% <100.00%> (ø)
Sources/ConsoleKitTerminal/Terminal/Terminal.swift	26.59% <ø> (ø)
.../ConsoleKitTerminal/Utilities/LoggerFragment.swift	80.30% <ø> (ø)
Sources/ConsoleKitCommands/Base/CommandGroup.swift	87.27% <50.00%> (+2.78%)	⬆️
Sources/ConsoleKitCommands/Base/AnyCommand.swift	0.00% <0.00%> (ø)
...tCommands/Deprecated/MergedAsyncCommandGroup.swift	0.00% <0.00%> (ø)
Sources/ConsoleKitTerminal/Terminal/ANSI.swift	83.87% <36.36%> (-3.77%)	⬇️