Rename PSQLEncodingContext to PostgresEncodingContext

[fabianfett]

See #224, #225

[codecov-commenter]

Codecov Report

Merging #227 (0b5b9f0) into main (c98c808) will increase coverage by 4.08%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##             main     #227      +/-   ##
==========================================
+ 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% <ø> (+4.08%)	⬆️

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

Impacted Files	Coverage Δ
...s/PostgresNIO/New/Data/Array+PostgresCodable.swift	94.68% <ø> (+1.06%)	⬆️
...es/PostgresNIO/New/Data/Bool+PostgresCodable.swift	95.34% <ø> (+4.65%)	⬆️
...s/PostgresNIO/New/Data/Bytes+PostgresCodable.swift	73.52% <ø> (ø)
...es/PostgresNIO/New/Data/Date+PostgresCodable.swift	89.28% <ø> (ø)
...PostgresNIO/New/Data/Decimal+PostgresCodable.swift	74.19% <ø> (+6.45%)	⬆️
...s/PostgresNIO/New/Data/Float+PostgresCodable.swift	76.66% <ø> (+3.33%)	⬆️
...ces/PostgresNIO/New/Data/Int+PostgresCodable.swift	30.71% <ø> (+5.22%)	⬆️
...es/PostgresNIO/New/Data/JSON+PostgresCodable.swift	100.00% <ø> (ø)
...ostgresNIO/New/Data/Optional+PostgresCodable.swift	83.33% <ø> (ø)
...IO/New/Data/RawRepresentable+PostgresCodable.swift	82.35% <ø> (ø)
... and 35 more

[gwynne]

What I'll never understand is where you find the hours in the day to make these kinds of changes, Fabian. It must take you forever to do all this!