BLOOM minor changes on tokenizer
# What does this PR do?

- Attempts to fix minor issues with the BloomTokenizer
- Remove unused args
- Added a new attribute on `TokenizerTesterMixin` for models that are not agnostic to sequence length (typically models that use ALiBi positional embeddings)

Still need to discuss if it is worth it to force the padding side to the left

cc @SaulLu 
_The documentation is not available anymore as the PR was closed or merged._<|||||>We may merge this at the same time as https://github.com/huggingface/transformers/pull/17837 to make it a patch release of minor fixes<|||||>Let's not add a new attribute and change the common tests for one model only. You can override the test in the subclass of the main model tester, leaving the common tests as they are.