Move all generated files from "tests" to "runtime"

[Леонид Черненко]

There is no need to store any generated files directly in "tests" folder.

Both "_output" and "_support/generated" folders with all content should be placed in "runtime/tests" folder.

There should be as minimum files as possible in "tests", to simplify understanding and usage.

[Anton Samoylenko]

This issue probably should be in yiisoft/app, because I don't see test here

[Alexander Makarov]

Moved.

[Dmitriy Derepko]

I think only _output can be placed in runtime/tests/_output.
_generated used for IDE hints.