Bufferize OpenFHE backend pipeline

[j2kun]

After #2975 I want to also bufferize the OpenFHE backend. I suspect that along the way it will be easier to migrate it to emitc simultaneously, rather than do it in two steps.

[j2kun]

After some conversations with colleagues trying to use HEIR, I now suspect the OpenFHE code emitter generates code that leaks memory, and that the combination of bufferization and migrating the emitter to use emitC would fix it.