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

[weiwei chen via llvm-commits]

weiweichen 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.

Sound good! Thank you for investigating this! I'll wait.

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