[Build] Core packages are not .NET Standard 2.0 anymore

[tebjan]

Release Type: Official Release/GitHub (please choose appropriate option)

Release

Version: Version number and/or git branch

4.1.0.1734

Describe the bug The packages that can be .NET Standard should be so. This is a breaking change and forces libraries to be .NET 6 that have been .NET Standard. Also existing libraries cannot update to latest Stride.

To Reproduce Steps to reproduce the behavior:

1. Reference Stride.Core.Mathematics in a .NET Standard library.

Expected behavior Nugets can be referenced.

Screenshots

[manio143]

I vaguely remember there was some breaking change to .NET APIs used in Stride.Core after moving to net5 that wasn't compatible with netstandard2.0 and since everything depends on Stride.Core that also had to be upgraded.