[SUGGESTION] Upgrade Framework dependencies

[JKamsker]

This issue is just for keeping track of why we should upgrade the dependencies of the project from net4.5;netstandard1.3;netstandard2.0 to newer versions.

• Microsoft officially doesnt support part of the frameworks anymore
• Span support, tho it can be fixed using the System.Memory package

Open Questions:

• Do polyfills affect newer versions that have the required apis already implemented? (will the polyfill be present in those cases?)

And ofcourse, we would to bump atleast a minor version for that.

Related:

• [♻️Housekeeping] Remove BufferPool class and use .net implementation #2508

[ngoquoctoandev]

I also agree with your point of view. In an ever-evolving and constantly changing technological world, I think targeting the latest development frameworks would be more appropriate. For example, .NET 8

[Joy-less]

This pull request will replace support for .NET 4.5 and .NET Standard 1.3 with support for .NET Standard 2.0, .NET Standard 2.1, .NET 8.0 and .NET 9.0 if it is merged. But it's possible that framework changes will only happen in LiteDB v6+.