Remove Ply and update to FSharp 6 #807

Job	Run time
fable-npm-build (ubuntu-latest, 18)	2m 4s
fable-npm-build (ubuntu-latest, 20)	2m 10s
build-devcontainer	9m 0s
dotnet-build (Debug, ubuntu-latest)	3m 4s
fable-npm-build (ubuntu-latest, latest)	2m 4s
dotnet-build (Debug, windows-latest)	5m 8s
fable-python-build (ubuntu-latest, 3.10)	3m 20s
fable-npm-build (windows-latest, 18)	5m 40s
fable-python-build (ubuntu-latest, 3.11)	2m 36s
dotnet-build (Debug, macOS-latest)	6m 12s
fable-npm-build (windows-latest, 20)	6m 35s
fable-python-build (ubuntu-latest, 3.12)	2m 52s
dotnet-build (Release, ubuntu-latest)	3m 4s
fable-npm-build (windows-latest, latest)	6m 32s
fable-python-build (windows-latest, 3.10)	3m 55s
dotnet-build (Release, windows-latest)	5m 40s
fable-npm-build (macOS-latest, 18)	3m 54s
fable-python-build (windows-latest, 3.11)	5m 17s
dotnet-build (Release, macOS-latest)	6m 37s
fable-npm-build (macOS-latest, 20)	3m 8s
fable-python-build (windows-latest, 3.12)	6m 6s
fable-npm-build (macOS-latest, latest)	3m 52s
fable-python-build (macOS-latest, 3.10)	3m 49s
fable-python-build (macOS-latest, 3.11)	3m 58s
fable-python-build (macOS-latest, 3.12)	4m 20s
	1h 50m 57s

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