Remove environment variables from gtest

[CAHEK7]

Remove environment variables from gtest (MIOPEN_TEST_ALL, MIOPEN_TEST_FLOAT_ARG, etc).
This must be done simultaneously for all the tests and this issue switches old ctest scheme to the new one.

It must be done after all the tests have been renamed in #3133 and new test wrapper has been implemented in #3132

[atamazov]

[Notice] @CAHEK7 Maybe it is worth creating an umbrella ticket for gtests (which should list all the tickets or other items to be done) in a proper order, along with theirs statuses and assignments.