Mitigate a conflict when using sentencepiece (#33327)
* test(tokenizers): add a test showing conflict with sentencepiece
This is due to the fact that protobuf C implementation uses a global
pool for all added descriptors, so if two different files add
descriptors, they will end up conflicting.
* fix(tokenizers): mitigate sentencepiece/protobuf conflict
When sentencepiece is available, use that protobuf instead of the
internal one.
* chore(style): fix with ruff
