Use `AlbertConverter` for FNet instead of using FNet's own converter
# What does this PR do?

**Edited: Finally using `AlbertConverter` directly because the slow tokenizers between `Albert` and `FNet` are basically identical. (FNet doesn't have `bos_token` and `eos_token` while Albert does, but this difference doesn't matter.)**

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This PR adds normalizer to `FNetConverter`, making `do_lower_case` and `keep_accents` options of `FNetTokenizerFast` work.

This normalizer is copied from that of `Albert` as FNetTokenizerFast is adepted from `Albert`.


https://github.com/huggingface/transformers/blob/3ea15d27832d47d44ad046c3a776c7b582b0984b/src/transformers/models/fnet/tokenization_fnet_fast.py#L57-L61

## Who can review?

Anyone in the community is free to review the PR once the tests have passed. Feel free to tag
members/contributors who may be interested in your PR.

@LysandreJik @SaulLu @sgugger 
@SaulLu if this looks good to you, feel free to merge