Upgrade to .NET 9.0 #303

Job	Run time
Test Cloud Framework	1m 55s
Test StringEnum Trimmed	33s
Timestamp	13s
Build Windows Shim	1m 7s
Build Windows UEFS	3m 24s
Build Windows Pass 1	6m 43s
Build Linux Shim	27s
Build macOS Shim	38s
Build macOS UEFS	1m 14s
Build and Test Libraries on Linux	7m 0s
Build and Test Libraries on Windows	10m 14s
Build Libraries on macOS	4m 46s
Build Linux Pass 1	6m 2s
Build macOS Pass 1	5m 7s
Build Linux Pass 2	6m 33s
Build macOS Pass 2	4m 9s
Build Windows Pass 2	6m 57s
Publish UET Container (with Wine)	40s
Publish UET Container	40s
Publish to GitHub	0s
Publish to NuGet	0s
Test Schema Generation	24s
Publish UEFS Container	0s
	1h 8m 46s

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