Update dotnet framework

[b-kelly]

This PR updates the dotnet target framework from netstandard2.0 to net8.0 (the latest LTS). Despite there being no breaking changes in the code itself, I think that updating the framework target is a breaking-ish change, so I also bumped the version from 6.0.2 to 7.0.0.

The reasons for updating the framework are as follows:

1. We needed to drop the Microsoft.AspNetCore.Html.Abstractions standalone package
   • the standalone packages are deprecated and are now shipped in the framework reference (further reading)
2. There are no longer any new versions of netstandard being shipped since there is now one unified framework (further reading)

[giamir]

This looks good to me @b-kelly.

I opened a very similar PR here on Friday that I then ended up closing since the pipeline issue turned out to be a different reason.

I think we might want to target 2 frameworks since in Core we are not yet on dotnet 8.
In Stacks.Razor we are doing the same (support both 6 and 8 - Samo helped with that a while back and I did the same for the PR I ended up closing).

Thank you

[b-kelly]

@giamir Good callout. I'll review the PR you had closed to ensure that we're properly supporting net6.0 as well (for now, it's EOL soon and I know folks are working on the migration as we speak).

[giamir]

@giamir Good callout. I'll review the PR you had closed to ensure that we're properly supporting net6.0 as well (for now, it's EOL soon and I know folks are working on the migration as we speak).

If we can target both frameworks without big headaches I would just do it to avoid having to coordinate. We can drop support for 6 later on. 🙂

[b-kelly]

@giamir Updating to target both was trivial. Ready for review!