reinitialize rewind buffer after loading game with achievements

[Jamiras]

Description

Fixes #15933.

Because the achievement state needs to be included in the rewind buffer, the rewind manager has to be reset after the achievements are loaded so it has the proper size of a per-frame state.

Prior to #15912 rewind was disabled after identifying the game being loaded, and then re-enabled after the game was loaded. Identifying the loaded game is an asynchronous call to the server, so rewind wouldn't be disabled immediately when the game was loaded. And when it was re-enabled, the per frame state size would include the achievement state.

With the changes in #15912, identifying the game is part of a library call to load a game, so rewind was being disabled earlier; too early. The achievement rcheevos_load handler is being called earlier in content_init than the rewind state initialization code, so rewind was getting re-enabled immediately and it was still enabled when the achievement code tried to re-enable it later. As a result, the rewind state manager was still expecting frames without achievement state, so when a frame was captured with achievement state, it was too big and the state manager would discard it.

Solution: Instead of disabling rewind when rcheevos_load is called, quickly toggle it off and back on once the achievements are loaded so the per-frame size is correct.

Related Issues

#15933

Related Pull Requests

n/a

Reviewers

@Sanaki

[dontsnm]

With some cores like Snes9x and genesis plus, rewind doesn't work with achievements enabled.

[brigcam]

still having this issue here, it seems to happen when a game has no achievements (eg on 32x After Burner has the issue, but Spider-Man works fine). I'm on git version 07de6d9. it seems the same behaviour described here: #15933 (comment)