Add fixability grade to the deprecations output

[goba]

In http:https://hojtsy.hu/blog/2019-may-24/analysis-top-uses-deprecated-code-drupal-contributed-projects-may-2019 I graded each deprecation into 4 categories:

1. Don't know
2. Only in dev version of core (should not be fixed yet)
3. In supported version of core (should be fixed for custom code, not for d.o projects)
4. In unsupported version of core (should be fixable, unless you have a really old core)

Now that phpstan provides the deprecation version number in the output, we can grade each one automatically. Especially once https://www.drupal.org/project/drupal/issues/3048498 is fixed this grading will become even more accurate.

Solution probably should not be in drupal-check, but some layer above it so other consumers of the libraries can use it. Eg. Upgrade status, the d.o drupalci integration, etc.

[goba]

The processing / result is a bit more complicated when you encounter contrib projects deprecating things and/or 3rd party dependencies doing the same, so those should be put in the "don't know" category IMHO.

[goba]

This has now been implemented in the dev version of Upgrade Status. 5 categories I came up with:

1. Ignore: deprecations to be removed for Drupal 10, ignore for now.
2. Later: deprecation to be acted on later (in supported core version for a contrib module, in a later version than the core you are using for custom modules).
3. Safe: in the version or an older version than your core for custom modules.
4. Old: deprecation in older unsupported core version (for contributed modules).
5. Uncategorized: for everything else, eg. random PHP errors.

I made the listing add a legend for the ones encountered in the concrete list.