fix: dir no longer panics when HOME and XDG_CONFIG_HOME are not set

[Two-Hearts]

This PR is for release-1.2 branch only.

This PR cherry picks the fix of issue #446 from main.

The fix:

• Removed the init() function from dir/path
• When userConfigDir() returns an error, instead of panic(err), default to the current directory instead
• Split loadUserPath() into two new functions used to setup and return the values for UserConfigDir and UserLibexecDir
• Added additional unit tests for the two new functions and to test the default directory is used when HOME is set to ""

[codecov[bot]]

Codecov Report

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

Project coverage is 81.34%. Comparing base (07b2508) to head (0e4fbf0). Report is 1 commits behind head on release-1.2.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## release-1.2 #451 +/- ## =============================================== + Coverage 81.21% 81.34% +0.12% =============================================== Files 32 32 Lines 2279 2283 +4 =============================================== + Hits 1851 1857 +6 + Misses 299 298 -1 + Partials 129 128 -1 ```

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