Make PostgresEncodingContext & PostgresDecodingContext public

[fabianfett]

Motivation

We want to open up our new API

Changes

• Make PostgresEncodingContext public
• Make PostgresDecodingContext public

Result

Smaller future open up PRs.

[codecov-commenter]

Codecov Report

Merging #243 (06002b0) into main (ef425af) will increase coverage by 4.03%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main     #243      +/-   ##
==========================================
+ Coverage   39.57%   43.61%   +4.03%     
==========================================
  Files         115      115              
  Lines        9479     9486       +7     
==========================================
+ Hits         3751     4137     +386     
+ Misses       5728     5349     -379     

Flag	Coverage Δ
unittests	43.61% <100.00%> (+4.03%)	⬆️

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

Impacted Files	Coverage Δ
Sources/PostgresNIO/New/PostgresCodable.swift	91.66% <100.00%> (ø)
...ces/PostgresNIO/New/PostgresRow-multi-decode.swift	4.44% <0.00%> (+0.19%)	⬆️
...es/PostgresNIO/Connection/PostgresConnection.swift	11.83% <0.00%> (+0.75%)	⬆️
Sources/PostgresNIO/Data/PostgresRow.swift	50.00% <0.00%> (+1.02%)	⬆️
...s/PostgresNIO/New/Data/Array+PostgresCodable.swift	94.73% <0.00%> (+1.05%)	⬆️
...rces/PostgresNIO/New/Extensions/Logging+PSQL.swift	19.60% <0.00%> (+1.42%)	⬆️
...ostgresNIO/Deprecated/PostgresMessageDecoder.swift	95.45% <0.00%> (+2.27%)	⬆️
...es/PostgresNIO/New/PSQLBackendMessageDecoder.swift	93.28% <0.00%> (+2.98%)	⬆️
...urces/PostgresNIO/New/Messages/ErrorResponse.swift	32.30% <0.00%> (+3.07%)	⬆️
Sources/PostgresNIO/New/PostgresCell.swift	96.77% <0.00%> (+3.22%)	⬆️
... and 21 more

[gwynne]

👍