[mlir][conversion] NFC - Relax convert-cf-to-llvm and finalize-memref-to-llvm...

[mlir][conversion] NFC - Relax convert-cf-to-llvm and finalize-memref-to-llvm to also work on non-builtin module ops

This is a prerequisite for unentangling LowerGpuOpsToNVVMOps which explicitly populates its conversion with
`populateControlFlowToLLVMConversionPatterns` and `populateFinalizeMemRefToLLVMConversionPatterns`.

However those patterns cannot be generally added to a pass anchored on a non-ModuleOp.

Instead, LowerGpuOpsToNVVMOps should stop including the world, in a future commit.

Differential Revision: https://reviews.llvm.org/D156860