`M0-1-9`: Add test for side effects in a different translation unit

[rcseacord]

There should be a test where the side-effecting and no-side effecting functions are in a different translation unit:

https://github.com/github/codeql-coding-standards/blob/9a23abab13bbf3a075dd5f4c1372b93bfcb211e4/cpp/autosar/test/rules/M0-1-9/test.cpp#L1

What is the expected behavior in such as case?