Move all PostgresConnection code into one file

[fabianfett]

Motivation

When we merge PostgresConnection and PSQLConnection, I would love to see all changes in one file.

Changes

• Move all PostgresConnection code into one file

Result

• One file for PostgresConnection

[codecov-commenter]

Codecov Report

Merging #228 (13babe4) into main (7f53867) will increase coverage by 4.08%.
The diff coverage is 0.00%.

@@            Coverage Diff             @@
##             main     #228      +/-   ##
==========================================
+ Coverage   39.10%   43.19%   +4.08%     
==========================================
  Files         121      117       -4     
  Lines        9315     9322       +7     
==========================================
+ Hits         3643     4027     +384     
+ Misses       5672     5295     -377     

Flag	Coverage Δ
unittests	43.19% <0.00%> (+4.08%)	⬆️

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

Impacted Files	Coverage Δ
...es/PostgresNIO/Connection/PostgresConnection.swift	0.00% <0.00%> (ø)
...s/PostgresNIO/New/Data/Array+PostgresCodable.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	30.00% <0.00%> (+2.10%)	⬆️
...s/PostgresNIO/Message/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%)	⬆️
...s/PostgresNIO/New/Data/Float+PostgresCodable.swift	76.66% <0.00%> (+3.33%)	⬆️
Sources/PostgresNIO/New/PSQLBackendMessage.swift	96.63% <0.00%> (+3.36%)	⬆️
... and 21 more

[gwynne]

👍