Improve dataProvider annotation autocomplete

[Koc]

It is better suggest public non-test method for @dataProvider annotation, For now it completes class names.

[stof]

Might be unnecessary as this autocompletion has been improved in PHPStorm itself for the next release: https://youtrack.jetbrains.com/issue/WI-37542

[Koc]

indeed. Will check

[stof]

Well, AFAIK, the EAP for 2018.1 has not started yet, as they are finishing the 2017.3 release. And the issue says that this improvement is fixed only in 2018.1