vocab : add special infill tokens for CodeLlama (#11850)

vocab : add special infill tokens for CodeLlama (#11850)

* vocab : add special infill tokens for CodeLlama

The commit adds the following special tokens for CodeLlama infill:
- `▁<PRE>`
- `▁<SUF>`
- `▁<MID>`

The motivation for this is that currently the infill example uses
CodeLlama as a suggested model. But when using this model the following
error is generated:
```console
/llama.cpp-debug/examples/infill/infill.cpp:165: GGML_ASSERT(llama_vocab_fim_pre(vocab) >= 0) failed

Could not attach to process.  If your uid matches the uid of the target
process, check the setting of /proc/sys/kernel/yama/ptrace_scope, or try
again as the root user.  For more details, see /etc/sysctl.d/10-ptrace.conf
ptrace: Operation not permitted.
No stack.
The program is not being run.
305251 Aborted                 (core dumped)
./build/bin/llama-infill -t 10 -ngl 0 -m models/codellama-13b.Q5_K_S.gguf \
  -c 4096 --temp 0.7 --repeat_penalty 1.1 -n 20 \
  --in-prefix "def helloworld():\n    print(\"hell" \
  --in-suffix "\n   print(\"goodbye world\")\n    "
```

* squash! vocab : add special infill tokens for CodeLlama

Add _<EOT> as well.