…dapters into dev/test-refactoring

- reorder directory structure to separate testing models and adapter methods (needs further refactoring for separating tests that are extecuted for each model vs tests that are just run once)
- remove all model tests except albert for now (will be readded once final design is agreed on)
- refactor albert adapter test class to group test mixins in categories which are then displayed accordingly by test viewer
- adjust imports to reflect new directory structure

- refactor generate_test into base test class and adapt parallel generate test accordingly
- refactor lm head selection into own method
- create utils file for utility methods and adapt imports accordingly
- remove is_speech_model flags
- replace redundant attributes and methods
- enforce proper method naming conventions

This reverts commit b390d61.

- Re-add bart adapter method tests
- Remove duplicate added tests
- In conversion test refactor model specific if else statements into model test class

- deberta
- debertav2
- distilbert
- electra
- encoder-decoder
- llama
- mbart
- mistral
- mt5
- plbart
- roberta

- introduce parameter to cut down on makefile commands
- draw out tests that are not executed on every model into a seperate directory
- move the adapter method test implemenations into the method tests directory
- rename files for more clarity

- test was previously not included in testbase -> exclude it also now
- revert debugging changes

…/test-refactoring

- Add new test adding section to README and correct typos
- Decide on more expressive file names
- Save naming script for now, can be removed during Review

- Merge branch 'main' into dev/test-refactoring
- Adress review comments
- make style, make quality

…pported tests

-> Will be moved to separate issue

- for this a new dedicated issue can be found here: adapter-hub#785