Support large stack frames/offsets in GHCi bytecode interpreter

Bytecode instructions like PUSH_L (push a local variable) contain
an operand that refers to the stack slot. Before this patch, the
operand type was SmallOp (Word16), limiting the maximum stack
offset to 65535 words. This could cause compiler panics in some
cases (See #22888).

This patch changes the operand type for stack offsets from
SmallOp to Op, removing the stack offset limit.

Fixes #22888

(cherry picked from commit 564164ef)