Consider removing CROSSGEN_COMPILE define and the CrossGen binary #53007
Description
Now that CrossGen2 has replaced CrossGen, we should consider removing code guarded by the following defines:
- Remove code guarded by CROSSGEN_COMPILE #57657
- Remove code guarded by FEATURE_NATIVE_IMAGE_GENERATION #57658
- Remove code guarded by FEATURE_READYTORUN_COMPILER (outside of the coreclr/jit directory. It is still used there) #57659
- Remove code guarded by FEATURE_PREJIT #57660
- Remove code guarded by FEATURE_NGEN_RELOCS_OPTIMIZATIONS #57661
- Remove PlainPointer/RelativePointer/RelativeFixupPointer #57706