feat: execute INFORMATION_SCHEMA in single-use transaction

[olavloite]

Queries referencing the INFORMATION_SCHEMA must use a single-use read-only
transaction. If such a query is executed during a (read/write) transaction, it
will return a specific error. This error is now detected by PGAdapter and the
query is retried in a separate single-use read-only transaction.

This behavior is needed for TypeORM.

[codecov]

Codecov Report

Merging #276 (b614da6) into postgresql-dialect (b80069d) will increase coverage by 0.05%.
The diff coverage is 94.73%.

@@                   Coverage Diff                    @@
##             postgresql-dialect     #276      +/-   ##
========================================================
+ Coverage                 82.48%   82.53%   +0.05%     
- Complexity                 1293     1294       +1     
========================================================
  Files                       106      107       +1     
  Lines                      4476     4495      +19     
  Branches                    550      553       +3     
========================================================
+ Hits                       3692     3710      +18     
- Misses                      599      600       +1     
  Partials                    185      185              

Flag	Coverage Δ
all_tests	82.53% <94.73%> (+0.05%)	⬆️

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Impacted Files	Coverage Δ
...ogle/cloud/spanner/connection/ResultSetHelper.java	50.00% <50.00%> (ø)
...panner/pgadapter/statements/BackendConnection.java	90.93% <100.00%> (+0.44%)	⬆️

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