Remove all warn-concurrency warnings

[fabianfett]

Patch to remove all concurrency warnings.

[fabianfett]

This creates a nasty warning in macOS:

Conformance of 'JSONDecoder' to 'Sendable' is only available in macOS 13.0 or newer

[codecov-commenter]

Codecov Report

Merging #408 (8515d87) into main (abca6b3) will increase coverage by 0.00%.
Report is 1 commits behind head on main.
The diff coverage is 45.61%.

❗ Current head 8515d87 differs from pull request most recent head a1e04ea. Consider uploading reports for the commit a1e04ea to get more accurate results

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #408   +/-   ##
=======================================
  Coverage   49.03%   49.04%           
=======================================
  Files         108      108           
  Lines        8845     8874   +29     
=======================================
+ Hits         4337     4352   +15     
- Misses       4508     4522   +14     

Files	Coverage Δ
.../Connection/PostgresConnection+Configuration.swift	49.29% <ø> (ø)
...es/PostgresNIO/Message/PostgresMessage+Error.swift	0.00% <ø> (ø)
Sources/PostgresNIO/New/NotificationListener.swift	74.22% <100.00%> (+0.26%)	⬆️
Sources/PostgresNIO/New/PSQLError.swift	80.00% <ø> (ø)
Sources/PostgresNIO/New/PSQLRowStream.swift	86.00% <100.00%> (-0.05%)	⬇️
Sources/PostgresNIO/New/PSQLTask.swift	78.12% <ø> (ø)
...urces/PostgresNIO/New/PostgresChannelHandler.swift	84.77% <100.00%> (+0.15%)	⬆️
Sources/PostgresNIO/New/PostgresCodable.swift	95.23% <ø> (ø)
Sources/PostgresNIO/PostgresDatabase.swift	0.00% <ø> (ø)
...es/PostgresNIO/Utilities/PostgresJSONDecoder.swift	50.00% <100.00%> (+50.00%)	⬆️
... and 5 more

[fabianfett]

Those breaking changes are false positives:

15 breaking changes detected in PostgresNIO:
  💔 API breakage: func PostgresConnection.query(_:logger:file:line:_:) is now with @preconcurrency
  💔 API breakage: func PostgresConnection.withConnection(_:) is now with @preconcurrency
  💔 API breakage: func PreparedQuery.execute(_:_:) is now with @preconcurrency
  💔 API breakage: protocol PostgresDatabase has generic signature change from  to <Self : Swift.Sendable>
  💔 API breakage: protocol PostgresDatabase is now with @preconcurrency
  💔 API breakage: protocol PostgresDatabase has added inherited protocol Sendable
  💔 API breakage: func PostgresDatabase.prepare(query:handler:) is now with @preconcurrency
  💔 API breakage: func PostgresDatabase.query(_:_:onMetadata:onRow:) is now with @preconcurrency
  💔 API breakage: func PostgresDatabase.simpleQuery(_:_:) is now with @preconcurrency
  💔 API breakage: protocol PostgresJSONDecoder has generic signature change from  to <Self : Swift.Sendable>
  💔 API breakage: protocol PostgresJSONDecoder is now with @preconcurrency
  💔 API breakage: protocol PostgresJSONDecoder has added inherited protocol Sendable
  💔 API breakage: protocol PostgresJSONEncoder has generic signature change from  to <Self : Swift.Sendable>
  💔 API breakage: protocol PostgresJSONEncoder is now with @preconcurrency
  💔 API breakage: protocol PostgresJSONEncoder has added inherited protocol Sendable