Allow optionally taking full snapshots on a set interval in tracing mode

[MaartenS11]

This allows hybrid snapshot/tracing schemes where you trace most of the execution but still take snapshots every now and then to avoid expensive re-execution.

Example 6103010101000f0000:

  61 03 01 01 01 00 0f 00 00                                                                                                                                                                                                                                                                                               
  │  │  │  │  │  └──────────── checkpointInterval (big-endian u32) = 0x000f0000 = 983 040                                                                                                                                                                                                                                  
  │  │  │  │  └─────────────── checkpoint_state[0] = pcState (0x01)                                                                                                                                                                                                                                                       
  │  │  │  └────────────────── checkpoint_state_size (LEB128) = 1                                                                                                                                                                                                                                                         
  │  │  └───────────────────── min_return_values (LEB128) = 1                                                                                                                                                                                                                                                           
  │  └──────────────────────── policy = 3 → checkpointing                                                                                                                                                                                                                                                               
  └─────────────────────────── interruptSetSnapshotPolicy (0x61)