ZJIT: Track guard shape exit ratio (#15052)

new ZJIT stats excerpt from liquid-runtime: 
```
    vm_read_from_parent_iseq_local_count:        10,909,753
    guard_type_count:                            45,109,441
    guard_type_exit_ratio:                             4.3%
    guard_shape_count:                           15,272,133
    guard_shape_exit_ratio:                           20.1%
    code_region_bytes:                            3,899,392
```

lobsters
```
guard_type_count:                            71,765,580
guard_type_exit_ratio:                             4.3%
guard_shape_count:                           21,872,560
guard_shape_exit_ratio:                            8.0%
```

railsbench
```
guard_type_count:                            117,661,124
guard_type_exit_ratio:                              0.7%
guard_shape_count:                            28,032,665
guard_shape_exit_ratio:                             5.1%
```

shipit
```
guard_type_count:                            106,195,615
guard_type_exit_ratio:                              3.5%
guard_shape_count:                            33,672,673
guard_shape_exit_ratio:                            10.1%
```

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