Add option to sort tests based on information from @small, @medium, and @large

[sebastianbergmann]

• Tests annotated with @small should be run before tests annotated with @medium
• Tests annotated with @medium should be run before tests annotated with @large
• Tests annotated with @large should be run before tests not annotated with @small, @medium, or @large

[localheinz]

Should this be an additional sorting strategy, or the default?

[sebastianbergmann]

Additional sorting strategy, of course. Sorry for not being clear.

[epdenouden]

I'll make this tomorrow, if nobody is working on it already. It's a nice little reprieve from the data providers.

[epdenouden]

Something is wrong with the execution sorting as --order-by=depends,reverse in TestCaseTest. It was an artifact of how TestCaseTest is set up and interaction between some globals-backup behaviour. Has something to do with

final class TestCaseTest extends TestCase
{
    // [...]
    protected $backupGlobalsBlacklist = ['i', 'singleton'];
    // [...]
}

and was fixed by adding a @depends between tests that are testing globals backup in sequence.

[epdenouden]

Let me know if you'd rather have a pull request based on 8.2 :)