relax configuration file matching logic

[elfkuzco]

Rationale

Configuration files were matched explicitly as <country_code>.conf. This PR allows configuration files to contain additional characters that often tend to provide more information. For instance, mullvad configs are often named in the form <country_code>-<city>-<interface>.conf

Changes

• Allow configuration files to contain additional characters during selection.
• Randomize selection process to ensure any city/isp configuration file can be chosen and not just the first that matches the pattern.
• Remove check for IP country code against the test country code. Often times, country names from the IP lookup are not the standard names and pycountry fails to get the proper code. This check would cause such tests to be skipped even though they were the right configuration files.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 72.45%. Comparing base (81c60e9) to head (b2b9e8f). Report is 1 commits behind head on main.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #24 +/- ## ======================================= Coverage 72.45% 72.45% ======================================= Files 27 27 Lines 748 748 Branches 65 65 ======================================= Hits 542 542 Misses 195 195 Partials 11 11 ```

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