Do not unlink all sends on GC

[guillep]

We are losing PIC and monomorphic type information on each full GC.
This PR tries to avoid unlinking on each GC to see if there is a side effect.

[privat]

Nothing seems broken, but cache invalidation is one of the two hardest things in computer science. :)

The commit that introduced this mandatory callsite flush (among so many things) is 81fc34e.

[PalumboN]

There are two (possible) related failing tests:

VM Unit Tests / testOnStackReplacementForLongRunningVectorAddMethod(#ISA->#IA32 #wordSize->4) – MacOSX64.VMMakerTests.JitTests.VMJitMethodTest
<1s
VM Unit Tests / testMemoryAccessExceptionHandledTimeoutIsRespected(#ISA->#aarch64 #wordSize->8) – MacOSX64.VMMakerTests.JitTests.VMMachineSimulatorTest
1m 6s

The commit that introduces the unlink-send behaviour is what Jean said. And the call from preGCAction: appeared here 7c0d0ab#diff-715172f5f9bc44477ac2dc857665367d6e38210cc77747ad5ea4da441814ca4a

[guillep]

Tests are green