[One .NET] workarounds for F#

[jonathanpeppers]

Context: #5040

Using F# in .NET 6, there are quite a few outstanding issues we have workarounds in place for:

• NRE in linker: Linker fails for F# projects in .NET 5+ linker#1448
• $(ProduceReferenceAssembly) breaks F# compilation: .NET 5: can't build F# projects sdk#12954

[jonathanpeppers]

We can close this, these are fixed:

• Linker fails for F# projects in .NET 5+ linker#1448
• .NET 5: can't build F# projects sdk#12954

We don't set $(ProduceReferenceAssembly) with F# projects in tests anymore either: 61e1dc9