Switch GTest type from integration testing to unit testing.

[CAHEK7]

Some of the test in a current test suite are intended to be unit tests, but for historical reasons they were implemented as integration, which included whole library pipeline, but limited algorithm applicability using environmental variables.
Those tests must be rewritten as unit tests calling particular algorithms directly.

The test driver and string arguments must be removed.

A short, but not complete, list of the tests:

1. smoke_* tests, for example: https://github.com/ROCm/MIOpen/blob/develop/test/gtest/smoke_solver_ConvAsmImplicitGemmGTCDynamicFwdDlopsNCHWC.cpp
2. regression_* tests, for example: https://github.com/ROCm/MIOpen/blob/develop/test/gtest/regression_half_vega.cpp
3. various algorithms tests, has to be defined, for example: https://github.com/ROCm/MIOpen/blob/develop/test/gtest/reduce_custom_fp32.cpp