[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 I am investigating how much work needs to be done for the context ownership change.
I'll let you know by the end of the day (EST) about how it goes.
@weiweichen I understand the frustration, but this is an issue that has been gone unsolved for a while now. Even with the context issue fixed I don't think there's a guarantee the move constructor will work without segfaulting, and as @arsenm said, it will only add to the things patched haphazardly in MMI.

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