In a real 3DS, threads that call svcSyncRequest are put to sleep until the server responds via svcReplyAndReceive. Our HLE services don't implement this mechanism and are effectively immediate from the 3DS's point of view. This commit makes it so that we at least simulate the IPC delay.
Specific HLE handlers might need to put their callers to sleep for a longer period of time to simulate IO timings. This is their responsibility but doing so is currently not implemented.
See https://gist.github.com/ds84182/4a7690c5376e045cab9129ca4185bbeb for a test that was not passing before this commit.
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