Consolidate tests in a single location

[kurapov-peter]

Let's keep it clean

[ciyongch]

Separating the gtests and lit tests seems more reasonable? And this structure is what upstream MLIR did?

[Menooker]

what about a structure like this?

tests
       \
        dnnl
               \
                 dnnl tests
        mlir    <-------- file structure kept same as upstream
              \
                tests
                       \
                         mlir lit tests
                unittest
                        \
                          mlir unittests
                lit.cfg.py
                lit.site.cfg.py.in

And we may move the tests/lit.cfg.py tests/lit.site.cfg.py.in into tests/mlir/tests, and keep the directory unittest out of mlir/tests, to keep it the same structure of MLIR? I suppose there will be some changes needed in tests/lit.cfg.py tests/lit.site.cfg.py.in to update the paths for llvm-lit.

[kurapov-peter]

what about a structure like this?

Yeah, sounds good, I've restructured it in a similar way and added a note. Now mlir strictly follows upstream structure.