Use .NET 8 SDK to add .NET 8 target

[atifaziz]

This PR adds the .NET 8 target (requiring SDK upgrade to 8.0 too), primarily to address #1012.

This PR overlaps with #1039 from @viceroypenguin, which was done in parallel. Any differences will be consolidated here.

[viceroypenguin]

Will read some more later.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (97dbe98) 92.62% compared to head (663a61c) 92.62%.

❗ Current head 663a61c differs from pull request most recent head a3b88be. Consider uploading reports for the commit a3b88be to get more accurate results

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #1041   +/-   ##
=======================================
  Coverage   92.62%   92.62%           
=======================================
  Files         113      113           
  Lines        3419     3419           
  Branches     1055     1055           
=======================================
  Hits         3167     3167           
  Misses        189      189           
  Partials       63       63           

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[viceroypenguin]

a3b88be I thought about this too. I think I would qualify it as shipped, because even though there's no net8 version released, net8 consumers are consuming the net6 version which does have these methods. The important thing for the shipped/unshipped files is to have awareness via PR which things are added for the consumer in the next update. net8 consumers won't see these functions as new in net8, they'll just have net8 improvements.

[atifaziz]

@viceroypenguin Technically speaking, there's no difference but it just seems more honest and less confusing (especially for newcomers and pre-releases) to say it's unshipped for now.

The important thing for the shipped/unshipped files is to have awareness via PR which things are added for the consumer in the next update.

You might be saying the same thing, but I think it's more to avoid accidentally leaking something into the Public API. It could be eventually used for tacking too.