CU-862hyd5wx Rosalind down

[mart-r]

Rosalind is currently down. Some MedCAT tests rely on downloading a Vocab from medcat.rosalind.kcl.ac.uk/media/vocab.dat. When that is not available (currently returns 503), the tests fail since the Vocab is (understandably) unable to be loaded from the web response (the 503).

Because of the above, GHA/CIs keep failing due to the test failures.

What this PR does:

• Unify some of the Vocab downloads
  • Different tests did that separately using identical (or near identical) code
• Checks if the current tmp_vocab.dat has the 503 info
  • Which cannot be loaded
  • If so, tries fetching again
• If rosalind is unavailable
  • Generates a simple Vocab to use
• If rosalind is available and the current Vocab is the generated simple one
  • Downloads the new one

Made sure the tests run and succeed in 4 cases

• No tmp_vocab.dat
  • Running in new environment
• Existing simple, generated tmp_vocab.dat
  • Running in no-Rosalind situation
• The tmp_vocab.dat from Rosalind
  • Running in existing environment
  • Or Rosalind is available
• The tmp_vocab.dat that contains the 503
  • Running in existing environment
  • Where the tests were first run in a no-Rosalind situation

PS:
I've made sure all tests run and are successful with the generated Vocab. But I have not checked specifically whether they run in the same exact way they would be expected with the real Vocab. Because this generated Vocab has only 2 words, iterating over those may result in different behaviour compared to the real deal.

[mart-r]

I will be merging this in around 2h if nobody has any objections before that.

[mart-r]

It seems the Rosalind issue is now resolved. And the CIs have been re-run and are passing. So there's no rush in merging this PR.

So I'll leave it up until the new year in case someone has concerns.

But I think it's still good to have an alternative in case the link becomes unresponsive again at some point in the future. Plus, it'll be able to identify the 503 saved as the vocab and redownload (i.e when someone first ran the tests on a new environment and simply saved the 503).