Centralize NuGet package versions using Directory.Packages.props

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Implements centralized management of NuGet package versions across the project using the Directory.Packages.props file.

• Adds the Directory.Packages.props file to centrally manage NuGet package versions, setting ManagePackageVersionsCentrally to true and defining versions for all identified packages.
• Updates all .csproj files across various projects (NStore.BaseSqlPersistence, NStore.Core, NStore.Domain, NStore.Persistence.LiteDB, NStore.Core.Tests, NStore.Domain.Tests, NStore.Persistence.LiteDB.Tests, NStore.Persistence.Mongo.Tests, NStore.Persistence.Mongo, NStore.Persistence.MsSql.Tests, NStore.Persistence.MsSql, NStore.Persistence.Sqlite.Tests, NStore.Persistence.Sqlite, NStore.Quickstart, NStore.Tpl, and NStore.Tutorial) to reference the centralized package versions. This includes removing explicit version numbers from PackageReference elements and ensuring all projects reference the Directory.Packages.props for package version management.
• Ensures consistency in package version management across the solution, aligning with the initial task requirements.

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Project files does not compile due to errors

home/runner/work/NStore/NStore/src/NStore.Domain/NStore.Domain.csproj : error NU1009: The packages NETStandard.Library are implicitly referenced. You do not typically need to reference them from your project or in your central package versions management file. For more information, see https://aka.ms/sdkimplicitrefs [/home/runner/work/NStore/NStore/src/NStore.sln]