GLES unit tests were in the generic "unittests" directory.
In order to avoid confusion with Vulkan unit tests, the
GLES unit tests directory was renamed to GLESUnitTests.

Change-Id: Idc40f63daddc6f822207fc4a75dd037a46ae22a6
Reviewed-on: https://swiftshader-review.googlesource.com/c/21628Tested-by: Alexis Hétu <sugoi@google.com>
Reviewed-by: Nicolas Capens <nicolascapens@google.com>