Fix data race when calling `GetISO3166`

[georgepsarakis]

• Use parallelization in test cases in order to reproduce the problem and also detect such issues in the future.
• Enable race detector when running unit tests in Github Actions.
• Fix the data race by adding a package-level initialization function that populates the ISO3166 configurations on package initialization only.

[dongri]

@georgepsarakis Thank you LGTM