Lua: Show a future frame

[SuuperW]

This is an alternative to the invisible emulation changes made in #4592. (If this is merged, the unpausing thing from that PR still needs to be done.)

The old seekframe and invisibleemulation API methods have been removed, in favor of show_future.

Tool updates do not run during future emulation. Tools used to update during invisible emulation, which caused problems. But Lua would not update during seekframe (except that input and memory callbacks would run), so this matches old Lua behavior.

It is possible that a user would want Lua to run during future emulation (or in old terms, invisible emulation) but we can't know that. If we want to support this, it should be something such that scripts must opt-in to running during future emulation since most things should not run there. Maybe a new type of event.

Check if completed:

• I have run any relevant test suites
• I, the commit author, have read the licensing terms for contributors (last updated 2024-06-22) and am compliant