RISC-V 64 NCG: allocMoreStack probably deallocates too little and too much

Summary

The RISC-V NCG probably suffers from a similar issue as #25733 (closed) .

According to Note [extra spill slots] we have to emit deallocation instructions for non-local jumps. And, not for local jumps.

Currently, the code generator does the opposite:

• It generates deallocation instructions for jump tables (J_TBL) which are local jumps.
• It does not generate deallocation instructions for non-local jumps. In fact, we don't even distinguish between local and non-local jumps in the Instr instruction set.

Steps to reproduce

Unfortunately, the reproducer of #25733 (closed) does not hit 🙄 So, reproduction of the issue(s) is still to be done.

Expected behavior

• Don't emit deallocation instructions for J_TBL.
• Emit them for (to be introduced) non-local jumls (e.g. J).

• System Architecture: RISC-V 64 (NCG)