Unlike initlocal ldc_0 are propagated, also having smaller instruction footprint. Signal retry of cprop when we are adding such instructions, also in other cases. We could dynamically update the state, but let's not overcomplicate the cprop pass, for now.

On netcore, there are no context static fields so all special static fields are thread static. These thread static accessors are not very common, so just remove redundant opcodes for them, and use ldind/ldobj.vt and stind/stobj.vt instead.

These opcodes were used for loading a field of a VT var. This means the opcodes were loading a value from an immediate offset added to a var offset. We can use the standard MINT_MOV opcodes for this, however we need to resolve the offsets at the very end, so it doesn't interfere with other compilation passes, since the final offset is not the real offset of a variable, but rather an offset inside a VT var.

It was used to check for abort requests during backward branches. Also stop checking for abort requests in other places.

We include the safepoint in the instruction and also the immediate comparison value if possible. Doing the safepoint by default in branching opcodes is questionable since, in a typical program, forward branches are far more common than backward branches.We should really remove many of the branching opcodes. We now have the possibility to swap the src vars order, and use the opposite comparison instead.