Remove PSQLJSONDecoder

[fabianfett]

Motivation

While rewriting lot's of PostgresNIO internals in the last year, I created new types that very closely match existing types. This was a mistake. I should have tried everything to reuse existing types, and change them as needed.

Changes

⚠️ This PR extends API... minor version bump required.

• Remove PSQLJSONDecoder
• Extend PostgresJSONDecoder with a decode method based on ByteBuffer
• Provide a default implementation for the new decode method based on ByteBuffer to not break API
• Replace all uses of PSQLJSONDecoder with PostgresJSONDecoder

Result

Fewer types, easier API for adopters.

[codecov-commenter]

Codecov Report

Merging #216 (e4bf026) into main (cc07811) will increase coverage by 4.14%.
The diff coverage is 25.00%.

@@            Coverage Diff             @@
##             main     #216      +/-   ##
==========================================
+ Coverage   40.44%   44.59%   +4.14%     
==========================================
  Files         116      117       +1     
  Lines        7771     7775       +4     
==========================================
+ Hits         3143     3467     +324     
+ Misses       4628     4308     -320     

Flag	Coverage Δ
unittests	44.59% <25.00%> (+4.14%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
Sources/PostgresNIO/Postgres+PSQLCompat.swift	0.00% <ø> (ø)
...es/PostgresNIO/Utilities/PostgresJSONDecoder.swift	0.00% <0.00%> (ø)
Sources/PostgresNIO/New/PSQLRow.swift	63.15% <50.00%> (+2.63%)	⬆️
Sources/PostgresNIO/New/PSQLCodable.swift	100.00% <100.00%> (ø)
...urces/PostgresNIO/New/Data/Array+PSQLCodable.swift	94.68% <0.00%> (+1.06%)	⬆️
...rces/PostgresNIO/New/Extensions/Logging+PSQL.swift	19.60% <0.00%> (+1.42%)	⬆️
Sources/PostgresNIO/New/PSQLConnection.swift	31.68% <0.00%> (+1.98%)	⬆️
...s/PostgresNIO/Message/PostgresMessageDecoder.swift	95.45% <0.00%> (+2.27%)	⬆️
Sources/PostgresNIO/New/Data/Int+PSQLCodable.swift	20.26% <0.00%> (+2.61%)	⬆️
... and 22 more

[gwynne]

What I said on #215? That, but with more Infinity Improbability Drive side effects going on to drive home the idea that these are good PRs 😂