Reduce reliance on custom grown Jit implementation - NFC

This CL makes use of the standard LLVM LLJIT and removes the need for a custom JIT implementation within MLIR.

To achieve this, one needs to clone (i.e. serde) the produced llvm::Module into a new LLVMContext. This is currently necessary because the llvm::LLVMContext is owned by the LLVMDialect, somewhat deep in the call hierarchy.

In the future we should remove the reliance of serding the llvm::Module by allowing the injection of an LLVMContext from the top-level. Unfortunately this will require deeper API changes and impact multiple places. It is therefore left for future work.

PiperOrigin-RevId: 264737459