Progress in refactoring code and implementing unit tests

[kousuke-nakano]

What I am doing right now are:

• Adding intent(in, out, inout) statements,
• Adding use only statements, and
• Switching the bracket convention to the star convention in the declaration (e.g. real(8) -> real*8).
• Implementing unit tests for the updated codes if possible.

In this pull request, I have changed several codes in /src/m_common/

• WIP
• IntelOneAPI installation did not properly work (temporarily).

#12