[llvm] [CodeGen] Fix `MachineModuleInfo`'s move constructor to be more safe with `MCContext` ownership. (PR #104834)

[Matin Raayai via llvm-commits]

matinraayai wrote:

@weiweichen @arsenm #105541 addresses the issues raised in the review here.
If it proves challenging to merge due to `MCContext` management issues, we can merge only the first two items on the list regarding MMI's constructors. Let me know what you think.


https://github.com/llvm/llvm-project/pull/104834