Use testdrive for unit tests

[zoziha]

• [x] Use Fortran-lang/testdrive for unit tests;
• [x] Makefile adapted to testdrive accordingly.

Description

Only the file structure of the test part has been adjusted, and the testdrive has been adopted, and the actual test content has not changed.

In fact, fftpack's unit test content needs more:

• https://github.com/fortran-lang/fftpack/pull/18#discussion_r767423724
• https://github.com/fortran-lang/fftpack/pull/18#issuecomment-1023316720

[zoziha]

No functional changes in this PR, more tests are needed later, merge this PR first and use the testdrive library.