fix: Use .NET 9 SDK

[skarllot]

Pull Request

The issue or feature being addressed

• Packaging pipeline is failing

Details on the issue fix or feature implementation

• Use .NET 9 SDK
• Configure packaging pipeline to install .NET 6, 8 and 9

Confirm the following

• I started this PR by branching from the head of the default branch
• I have targeted the PR to merge into the default branch
• I have included unit tests for the issue/feature
• I have successfully run a local build

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 76.65%. Comparing base (3e632df) to head (8dcf969).
Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #323   +/-   ##
=======================================
  Coverage   76.65%   76.65%           
=======================================
  Files          14       14           
  Lines         347      347           
  Branches       32       32           
=======================================
  Hits          266      266           
  Misses         74       74           
  Partials        7        7           

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