Rename PSQLDecodable to PostgresDecodable

[fabianfett]

Motivation

The PSQL prefix is uncool for new public types.

Changes

• Rename PSQLDecodable to PostgresDecodable

[codecov-commenter]

Codecov Report

Merging #224 (24da8dd) into main (dd5b17c) will increase coverage by 4.08%.
The diff coverage is 10.52%.

@@            Coverage Diff             @@
##             main     #224      +/-   ##
==========================================
+ Coverage   39.10%   43.19%   +4.08%     
==========================================
  Files         121      121              
  Lines        9315     9322       +7     
==========================================
+ Hits         3643     4027     +384     
+ Misses       5672     5295     -377     

Flag	Coverage Δ
unittests	43.19% <10.52%> (+4.08%)	⬆️

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

Impacted Files	Coverage Δ
...urces/PostgresNIO/New/Data/Array+PSQLCodable.swift	94.68% <ø> (+1.06%)	⬆️
...es/PostgresNIO/New/Data/Optional+PSQLCodable.swift	83.33% <ø> (ø)
Sources/PostgresNIO/New/PSQLCodable.swift	96.00% <ø> (+4.00%)	⬆️
Sources/PostgresNIO/New/PSQLRow-multi-decode.swift	0.00% <0.00%> (ø)
Sources/PostgresNIO/New/PostgresCell.swift	96.77% <ø> (+3.22%)	⬆️
Sources/PostgresNIO/Postgres+PSQLCompat.swift	0.00% <ø> (ø)
Sources/PostgresNIO/New/PSQLRow.swift	59.37% <50.00%> (ø)
...rces/PostgresNIO/New/Extensions/Logging+PSQL.swift	19.60% <0.00%> (+1.42%)	⬆️
Sources/PostgresNIO/New/PSQLConnection.swift	30.00% <0.00%> (+2.10%)	⬆️
... and 27 more

[gwynne]

Darn it, Fabian, stop making me review these massive overcomplicated change sets! How's a person supposed to keep track of so many changes at once? 🤣 🤣 🤣 🤣 🤣