Fix try/catch control flow in eBPF and missing catch body in userspace

[SiyuanSun0736]

eBPF Control Flow Update

• Context Extension: Added current_catch_label to c_context to track the exit point of try blocks.
• Jump Mechanism: IRTry now generates a unique label emitted before the catch logic; IRThrow emits a goto to this label, preventing execution of subsequent instructions in the try block.

Userspace Backend Update

• Logic Realization: Replaced static placeholder comments in catch clauses with recursive calls to generate_c_instruction_from_ir.
• Code Generation: Instructions within catch_body are now concatenated and properly indented within the C switch statement.