Support .NET 8 and Separate SQL dependency

This release includes a community change to separate out the dependency on the SQL Client from within Dapper.Abstractions and separate that to a separate package Dapper.Abstractions.Sql, as well as adding an Oracle package Dapper.Abstractions.Oracle.

Also updated the project to include .NET 8 libraries in the package and deprecate .NET 7 support as it is now out of support