Improve error message when temporary folder cannot be safely determined

[robomics]

This PR introduces three changes:

• Improve the error message issued by hictk when the path to a temporary directory cannot be safely determined
• In case of errors, check whether the HICTK_CI env variable is defined - this is used to workaround known issues with tmp folders in the CI environment
• Avoid raising errors when there are issues with the tmpdir detection, and this clearly won't lead to any issues (e.g. when calling hictk --help)

Closes https://github.com/paulsengroup/hictk/issues/193

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 83.33333% with 3 lines in your changes missing coverage. Please review.

Project coverage is 85.12%. Comparing base (48341b4) to head (f41e476). Report is 29 commits behind head on main.

Files	Patch %	Lines
src/hictk/cli/cli_balance.cpp	66.66%	2 Missing :warning:
src/hictk/cli/cli_load.cpp	50.00%	1 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #210 +/- ## ========================================== + Coverage 85.10% 85.12% +0.02% ========================================== Files 120 120 Lines 10332 10355 +23 ========================================== + Hits 8793 8815 +22 - Misses 1539 1540 +1 ```

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