Final Prettier Test Migration

[Janther]

this is the final update for the tests to align us better with prettier's:
here we mostly update de code of each file to match prettier (while keeping same-ish logic but the same responsibilities)
The biggest changes are:

• tests/config/run-test.js: before we just ran all tests, now we have an array of functionalities to test, with a very descriptive name, and very clear rules to skip or run the test. There are 2 chances to skip tests, one is more general and declared in this list, and another more specific of each test that was added to each test.
• tests/config/test-{functionality}.js: each one of these tests now declares a test for their own functionality and describes a function to skip this test.
• getTestCase(): prettier doesn't set a default printWidth: 80 here but in its code itself. Removing this forces an update to every snapshot.

  parsers: ["slang"]
  - printWidth: 80
  -                                                                 printWidth: 80 |
  +                                                       printWidth: 80 (default) |