JSExportAttribute improvements #355

Job	Run time
build (windows-latest, net472, 20.x, Release)	6m 35s
build (windows-latest, net6.0, 20.x, Release)	5m 25s
build (windows-latest, net8.0, 18.x, Release)	7m 12s
build (windows-latest, net8.0, 20.x, Release)	7m 16s
build (macos-latest, net6.0, 20.x, Release)	9m 23s
build (macos-latest, net8.0, 18.x, Release)	11m 26s
build (macos-latest, net8.0, 20.x, Release)	5m 55s
build (ubuntu-latest, net6.0, 20.x, Release)	5m 9s
build (ubuntu-latest, net8.0, 18.x, Release)	4m 52s
build (ubuntu-latest, net8.0, 20.x, Release)	5m 17s
	1h 8m 30s

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