Remove the spurious dependency on AsyncKit

[gwynne]

These changes are now available in 1.52.0

Although each of the Fluent database drivers depends on AsyncKit for (poor) connection pooling, FluentKit itself does not need any of AsyncKit's services. It was only being used for some simple EventLoopFuture utilities, and wasn't even being reexported (thankfully). This removes the completely unnecessary dependency altogether.

Additional changes:

• The minimum required Swift version is now 5.10
• The code is now MemberImportVisibility-correct
• The MirrorBypass logic is now enabled in Swift 6.1

[codecov]

Codecov Report

Attention: Patch coverage is 2.77778% with 35 lines in your changes missing coverage. Please review.

Project coverage is 23.91%. Comparing base (788f4b9) to head (29ff170).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
Sources/FluentKit/Migration/Migrator.swift	0.00%	12 Missing ⚠️
...ntBenchmark/SolarSystem/GalacticJurisdiction.swift	0.00%	7 Missing ⚠️
...entBenchmark/Tests/PerformanceTests+Siblings.swift	0.00%	3 Missing ⚠️
Sources/FluentKit/Query/Builder/QueryBuilder.swift	0.00%	3 Missing ⚠️
...rces/FluentBenchmark/SolarSystem/SolarSystem.swift	0.00%	2 Missing ⚠️
...urces/FluentBenchmark/Tests/CompositeIDTests.swift	0.00%	2 Missing ⚠️
...FluentBenchmark/Tests/CompositeRelationTests.swift	0.00%	2 Missing ⚠️
Sources/FluentBenchmark/SolarSystem/Governor.swift	0.00%	1 Missing ⚠️
Sources/FluentBenchmark/Tests/FilterTests.swift	0.00%	1 Missing ⚠️
Sources/FluentBenchmark/Tests/SchemaTests.swift	0.00%	1 Missing ⚠️
... and 1 more

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #634      +/-   ##
==========================================
- Coverage   24.24%   23.91%   -0.33%     
==========================================
  Files         149      149              
  Lines        9397     9327      -70     
==========================================
- Hits         2278     2231      -47     
+ Misses       7119     7096      -23     

Files with missing lines	Coverage Δ
Sources/FluentBenchmark/Tests/ModelTests.swift	0.00% <ø> (ø)
Sources/FluentBenchmark/Tests/SQLTests.swift	0.00% <ø> (ø)
Sources/FluentKit/Migration/Migration.swift	0.00% <ø> (ø)
Sources/FluentKit/Model/MirrorBypass.swift	85.18% <ø> (+8.99%)	⬆️
Sources/FluentBenchmark/SolarSystem/Governor.swift	3.03% <0.00%> (ø)
Sources/FluentBenchmark/Tests/FilterTests.swift	0.00% <0.00%> (ø)
Sources/FluentBenchmark/Tests/SchemaTests.swift	0.00% <0.00%> (ø)
Sources/FluentSQL/SQLDatabase+Model.swift	64.51% <50.00%> (ø)
...rces/FluentBenchmark/SolarSystem/SolarSystem.swift	0.00% <0.00%> (ø)
...urces/FluentBenchmark/Tests/CompositeIDTests.swift	0.00% <0.00%> (ø)
... and 5 more

... and 5 files with indirect coverage changes

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