GetSchema implementation for Columns and Tables with unit tests.

[github-actions[bot]]

Package	Line Rate	Branch Rate	Health
Data.Common	70%	58%	✔
Data.Tests.Common	89%	58%	✔
Data.Csv	85%	83%	✔
Data.Xml	83%	79%	✔
Data.Common	72%	61%	✔
Data.Tests.Common	93%	64%	✔
Data.Json	84%	77%	✔
Data.Common	75%	63%	✔
Data.Tests.Common	94%	63%	✔
Data.Json	65%	56%	✔
EFCore.Common.Tests	93%	83%	✔
EFCore.Common	77%	56%	✔
Data.Common	46%	40%	➖
EFCore.Json	79%	50%	✔
EFCore.Common.Tests	90%	83%	✔
Data.Xml	55%	50%	➖
EFCore.Common	77%	56%	✔
Data.Common	41%	36%	➖
EFCore.Xml	79%	50%	✔
EFCore.Common.Tests	88%	83%	✔
EFCore.Csv	79%	50%	✔
EFCore.Common	77%	56%	✔
Data.Common	44%	38%	➖
Data.Csv	56%	46%	➖
Data.Common	1%	0%	❌
Summary	57% (10540 / 17269)	44% (2953 / 6561)	➖