refactor: Move SQLConnector into a separate module, for use by both SQLStream and SQLSink

[kgpayne]

Closes #1090

• refactor: Move SQLConnector into a separate module, for use by both SQLStream and SQLSink #1090

---

📚 Documentation preview 📚: https://meltano-sdk--1091.org.readthedocs.build/en/1091/

[kgpayne]

This commit doesn't change any logic. I simply moved the SQLConnector into a new sql module 🙂

[codecov]

Codecov Report

Attention: Patch coverage is 78.31325% with 54 lines in your changes missing coverage. Please review.

Project coverage is 83.46%. Comparing base (37595ec) to head (24464ae).
Report is 1039 commits behind head on main.

Files	Patch %	Lines
singer_sdk/connectors/sql.py	77.50%	37 Missing and 17 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1091      +/-   ##
==========================================
+ Coverage   83.43%   83.46%   +0.03%     
==========================================
  Files          40       42       +2     
  Lines        3846     3853       +7     
  Branches      657      657              
==========================================
+ Hits         3209     3216       +7     
  Misses        472      472              
  Partials      165      165              

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.