[lli] Add Orc greedy mode as -jit-kind=orc

In the existing OrcLazy mode, modules go through partitioning and outgoing calls are replaced by reexport stubs that resolve on call-through. In greedy mode that this patch unlocks for lli, modules materialize as a whole and trigger materialization for all required symbols recursively. This is useful for testing (e.g. D98785) and it's more similar to the way MCJIT works.