Add basic tests for applier

[timvaillancourt]

Description

This PR adds basic tests to a few funcs from go/logic/applier.go, also two small fixes were made based on findings in testing

Details:

• Added tests to func that don't use MySQL in go/logic/applier_test.go
• Removed extra spaces in sql. BuildDMLUpdateQuery() from go/sql/builder.go
• Modified applier.generateSqlModeQuery() to avoid duplicate commas:
  • Before example (double-comma):

    sql_mode = CONCAT(@@session.sql_mode, ',,NO_AUTO_VALUE_ON_ZERO')
    

  • After example:

    sql_mode = CONCAT(@@session.sql_mode, ',NO_AUTO_VALUE_ON_ZERO')
    

In case this PR introduced Go code changes:

• [x] contributed code is using same conventions as original code
• [x] script/cibuild returns with no formatting errors, build errors or unit test errors.