[mono] Refactor switch statements in process_bb to reduce redundancy

[kotlarmilos]

Description

The process_bb function in mini-llvm.c contains about 80 switch statements within switch (ins->opcode) {. The goal is to reduce code redundancy by introducing helper functions. To achieve this, the first step is to identify patterns and common operations within the switch cases. Each pattern should be encapsulated into a helper function.

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[kapilepatel]

I someone working on this? I would like to co-work.

[kotlarmilos]

Thanks, I believe no one is working on this at the moment. If you plan to propose changes, I suggest outlining your general approach here first to get feedback before submitting a PR.