feat: add PostgreSQL string pkeys support

[thiagotnunes]

Implement collations query for the PostgreSQL adapter to allow for String primary keys.

[codecov]

Codecov Report

Attention: Patch coverage is 97.22222% with 1 line in your changes missing coverage. Please review.

Project coverage is 52.03%. Comparing base (36961b4) to head (a57abcf).
Report is 20 commits behind head on main.

Files with missing lines	Patch %	Lines
...e/reader/io/jdbc/dialectadapter/ResourceUtils.java	93.75%	1 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##               main    #1905      +/-   ##
============================================
+ Coverage     44.81%   52.03%   +7.21%     
+ Complexity     3564     1304    -2260     
============================================
  Files           832      371     -461     
  Lines         49479    20336   -29143     
  Branches       5196     2054    -3142     
============================================
- Hits          22172    10581   -11591     
+ Misses        25656     9091   -16565     
+ Partials       1651      664     -987     

Components	Coverage Δ
spanner-templates	66.62% <97.22%> (+1.06%)	⬆️
spanner-import-export	∅ <ø> (∅)
spanner-live-forward-migration	74.86% <ø> (ø)
spanner-live-reverse-replication	75.55% <ø> (ø)
spanner-bulk-migration	84.53% <97.22%> (+0.33%)	⬆️

Files with missing lines	Coverage Δ
...jdbc/dialectadapter/mysql/MysqlDialectAdapter.java	99.61% <100.00%> (-0.02%)	⬇️
...ctadapter/postgresql/PostgreSQLDialectAdapter.java	97.28% <100.00%> (+10.13%)	⬆️
.../uniformsplitter/stringmapper/CollationMapper.java	97.27% <100.00%> (+0.05%)	⬆️
...e/reader/io/jdbc/dialectadapter/ResourceUtils.java	93.75% <93.75%> (ø)

... and 479 files with indirect coverage changes