Add JLJITLinkMemoryManager (ports memory manager to JITLink) (#60105)
Ports our RTDyLD memory manager to JITLink in order to avoid memory use
regressions after switching to JITLink everywhere (#60031). This is a
direct port: finalization must happen all at once, because it
invalidates all allocation `wr_ptr`s. I decided it wasn't worth it to
associate `OnFinalizedFunction` callbacks with each block, since they
are large enough to make it extremely likely that all in-flight
allocations land in the same block; everything must be relocated before
finalization can happen.