feat: show hints at startup for psql connections

[olavloite]

Automatically show hints for usage and options when PGAdapter receives a psql
connection.

[codecov]

Codecov Report

Merging #311 (4292046) into postgresql-dialect (9e4d391) will decrease coverage by 0.01%.
The diff coverage is 85.45%.

@@                   Coverage Diff                    @@
##             postgresql-dialect     #311      +/-   ##
========================================================
- Coverage                 83.17%   83.16%   -0.02%     
- Complexity                 1430     1444      +14     
========================================================
  Files                       109      111       +2     
  Lines                      4982     5072      +90     
  Branches                    640      650      +10     
========================================================
+ Hits                       4144     4218      +74     
- Misses                      628      637       +9     
- Partials                    210      217       +7     

Flag	Coverage Δ
all_tests	83.16% <85.45%> (-0.02%)	⬇️

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

Impacted Files	Coverage Δ
...ud/spanner/pgadapter/utils/ClientAutoDetector.java	88.00% <66.66%> (-4.69%)	⬇️
...e/cloud/spanner/pgadapter/utils/HintGenerator.java	77.77% <77.77%> (ø)
...d/spanner/pgadapter/wireoutput/NoticeResponse.java	80.00% <80.00%> (ø)
...gle/cloud/spanner/pgadapter/ConnectionHandler.java	75.18% <100.00%> (+0.37%)	⬆️
...om/google/cloud/spanner/pgadapter/ProxyServer.java	80.27% <100.00%> (ø)
...ud/spanner/pgadapter/metadata/OptionsMetadata.java	78.86% <100.00%> (+0.61%)	⬆️
...anner/pgadapter/wireprotocol/BootstrapMessage.java	96.07% <100.00%> (+0.62%)	⬆️
...spanner/pgadapter/wireprotocol/StartupMessage.java	86.36% <100.00%> (+0.31%)	⬆️

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