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

[Matt Arsenault via llvm-commits]

arsenm wrote:

> > This isn't big enough to call for an RFC
> 
> Not trying to be difficult, but I'm curious what is the criteria for API changing with an RFC. Is there a community guideline about this? 

I think it would be hard to write a specific rule. This case isn't changing the IR, and is only changing a niche mostly internal API.


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