Fix JIT+pystats crash: is_terminator fails for base opcodes

Two bugs when building with --enable-experimental-jit --enable-pystats:

1. `is_terminator()` uses `_PyUop_Uncached[opcode]` to map replicated
   variants back to base opcodes, but the array only contains entries
   for replicated variants (e.g. `_JUMP_TO_TOP_r00`). For base opcodes
   like `_JUMP_TO_TOP` itself, it returns 0, so the terminator is not
   recognized. This causes `effective_trace_length()` to hit
   `Py_FatalError("No terminating instruction")`.

   Fix: fall back to the raw opcode when `_PyUop_Uncached` returns 0.

2. `jit.c` references `jit_got_size` in `OPT_STAT_ADD` but the field
   is missing from `OptimizationStats` in `pystats.h`, causing a build
   failure.

   Fix: add the missing `jit_got_size` field.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: eendebakpt

Include/cpython/pystats.h

@@ -162,6 +162,7 @@ typedef struct _optimization_stats {
     uint64_t jit_code_size;
     uint64_t jit_trampoline_size;
     uint64_t jit_data_size;
+    uint64_t jit_got_size;
     uint64_t jit_padding_size;
     uint64_t jit_freed_memory_size;
     uint64_t trace_total_memory_hist[_Py_UOP_HIST_SIZE];

Python/optimizer.c

@@ -602,6 +602,9 @@ static int
 is_terminator(const _PyUOpInstruction *uop)
 {
     int opcode = _PyUop_Uncached[uop->opcode];
+    if (opcode == 0) {
+        opcode = uop->opcode;
+    }
     return (
         opcode == _EXIT_TRACE ||
         opcode == _DEOPT ||