Experimental OrcJITv2 support

[gmarkall]

For working on OrcJITv2 support.

Current status:

• Passes tests with LLVM 14.0.6
• Numba support needs work.
• MCJIT example ported to LLJIT works.

Current known to-do list:

• [ ] Add documentation.
• [ ] Invalidate modules passed to add_ir_module() since they're not usable after that.
• [X] Remove the hack to keep a global list of thread safe modules to keep them alive after compilation.
• [ ] Remove abort statements.
• [ ] Provide the resource tracker back to the caller of add_ir_module(), wrapped in something that removes it when it is garbage-collected.

Not todo:

• Implement an object cache. This will come later.