llama : recognize IBM Granite 3.3 FIM tokens (#12988)
The Granite's FIM tokens are very similar to Qwen's; it's just that
they use underscore instead of a dash. So <fim_middle> for example
instead of <fim-middle>.
Opening up tokenizer_config.json in ibm-granite/granite-3.3-8b-base
shows:
```
"<fim_prefix>",
"<fim_middle>",
"<fim_suffix>",
"<fim_pad>",
...
"<reponame>",
```
