Make check_init script more robust and clean inits
# What does this PR do?

This PR was triggered by the inits deactivating the formatter (see `wav2_vec2_with_lm` below) which was a bit sad. In one line, `check_inits.py` was unable to parse `_import_structure` initialized in one line, this PR addresses that and cleans many model inits.

HuBERT also contained some reference to Wav2Vec2FeatureExtractor, which should not be the case. This PR cleans that up as well.

_The documentation is not available anymore as the PR was closed or merged._