Make connections config consistent with Knex's config (breaking change)

[kabirbaidhya]

BREAKING CHANGE

• Connection config is made identical to the Knex's config. The only difference is we use only handful of those client and connection and we add id attribute for our internal purpose.
• Being consistent with Knex is important because we want to support the things Knex add out of the box, as much as possible.
• Programmatic API usage will break too - it expects type ConnectionConfig | ConnectionConfig[].

Checklist

• Update and test node-app-mssql example
• Update and test programmatic usage example
• Update connection id auto-generation logic when not given - making it numeric might be the only way there.

[codecov-io]

Codecov Report

Merging #65 into experimental will decrease coverage by 6.46%.
The diff coverage is 33.33%.

@@               Coverage Diff                @@
##           experimental      #65      +/-   ##
================================================
- Coverage         29.72%   23.25%   -6.47%     
================================================
  Files                27       27              
  Lines              1840     1694     -146     
  Branches            355      335      -20     
================================================
- Hits                547      394     -153     
- Misses             1277     1286       +9     
+ Partials             16       14       -2     

Impacted Files	Coverage Δ
src/config.ts	28.57% <7.69%> (-11.28%)	⬇️
src/util/db.ts	17.14% <75.00%> (-0.77%)	⬇️
...igration/source-types/SqlMigrationSourceContext.ts	23.52% <0.00%> (-20.07%)	⬇️
src/migration/service/migrator.ts	20.25% <0.00%> (-17.68%)	⬇️
src/util/promise.ts	15.09% <0.00%> (-15.82%)	⬇️
src/service/sqlRunner.ts	27.95% <0.00%> (-13.37%)	⬇️
src/service/execution.ts	14.08% <0.00%> (-10.34%)	⬇️
src/service/configInjection.ts	21.59% <0.00%> (-6.60%)	⬇️
src/migration/KnexMigrationSource.ts	84.21% <0.00%> (-6.12%)	⬇️
... and 8 more

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[kabirbaidhya]

Remaining TODO items and tests to be done in the subsequent PRs.