Update to .NET 9 SDK #519

Job	Run time
Build and Test (debug, net35, windows-latest)	7m 16s
Event File	7s
Build and Test (debug, net40, windows-latest)	7m 18s
Validate generated files	4m 8s
Build and Test (debug, All, windows-latest)	12m 26s
Build and Test (debug, All, ubuntu-latest)	5m 11s
Build and Test (debug, All, macos-latest)	7m 47s
Build and Test (release, net35, windows-latest)	7m 54s
Build and Test (release, net40, windows-latest)	7m 27s
Build and Test (release, All, windows-latest)	12m 35s
Build and Test (release, All, ubuntu-latest)	5m 11s
Build and Test (release, All, macos-latest)	14m 1s
	1h 31m 21s

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