fix(targets): missing begin()s related to SQLAlchemy 2.0

[andyoneal]

adds begin() to three other functions where schema is added or columns are altered. because of the changes made to auto-commit in SQLAlchemy 2.0, without begin() the ddl is rolled back.

matches style used in _create_empty_column()

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📚 Documentation preview 📚: https://meltano-sdk--1954.org.readthedocs.build/en/1954/

[codecov]

Codecov Report

Merging #1954 (ee948d3) into main (07198b0) will increase coverage by 0.07%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main    #1954      +/-   ##
==========================================
+ Coverage   87.01%   87.08%   +0.07%     
==========================================
  Files          59       59              
  Lines        5112     5112              
  Branches      827      827              
==========================================
+ Hits         4448     4452       +4     
+ Misses        468      465       -3     
+ Partials      196      195       -1     

Files Changed	Coverage Δ
singer_sdk/connectors/sql.py	84.15% <100.00%> (+1.32%)	⬆️

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[edgarrmondragon]

Thanks @andyoneal! This revealed some untested paths so I pushed tests to your branch.