Convert all NET7_0_OR_GREATER and NET8_0_OR_GREATER preprocessor directives to NET

[rajkumar-rangaraj]

It can be follow up, but you can potentially include it also here. Review alle conditional compilation. At least NET7_0_OR_GREATER and NET8_0_OR_GREATER. I think that all of them can be converted just to NET. There were decision to simplify condition where possible and remove exact versions.

Originally posted by @Kielek in #5832 (review)