[clang] [flang] [llvm] [mlir] Make MMIWP not have ownership over MMI + Make MMI Only Use an External MCContext (PR #105541)

[Arthur Eubanks via cfe-commits]

aeubanks wrote:

sorry for the delay

after looking at MMI/MCContext, I agree that MMI shouldn't own MCContext, but do we even need a reference from MMI to MCContext? they are different layers of codegen IIUC. if it's possible to completely separate them we should do that (please correct me if this doesn't make sense since I haven't spent too much time in codegen)

https://github.com/llvm/llvm-project/pull/105541