Increase .NET 8 compatibility

[bkoelman]

Reduce the required version of our dependency on Microsoft.CodeAnalysis to enable building with .NET 8 SDK v8.0.1xx, which is the version installed by the Ubuntu package manager.

See the version table at https://andrewlock.net/supporting-multiple-sdk-versions-in-analyzers-and-source-generators/ and the Ubuntu feed at https://launchpad.net/ubuntu/+source/dotnet8.

Fixes #1821.

QUALITY CHECKLIST

• Changes implemented in code
• Complies with our contributing guidelines
• N/A: Adapted tests
• N/A: Documentation updated

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 92.76%. Comparing base (c8abe25) to head (39f41ab).
⚠️ Report is 1 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #1822   +/-   ##
=======================================
  Coverage   92.76%   92.76%           
=======================================
  Files         437      437           
  Lines       14821    14821           
  Branches     2391     2391           
=======================================
  Hits        13749    13749           
  Misses        654      654           
  Partials      418      418           

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