Rename BytecodeOperandFlag to BytecodeOperandFlag8. The methods in
interpreter-assembler were missed in https://crrev.com/c/3857561.

Change-Id: I09383531e4d16e6e428a56feb76192156211dc81
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3867515
Commit-Queue: Patrick Thier <pthier@chromium.org>
Reviewed-by: Leszek Swirski <leszeks@chromium.org>
Cr-Commit-Position: refs/heads/main@{#82869}