splitted ltm- and stm-memory roots for FileHandler to avoid tmp-clear…

[Lukas113]

Split long-term-memory disk-cache root from short-term-memory. The reason for this change is because before a differentiation between the two use-cases regarding the root-directory was not possible. Therefore, the default root-dir /tmp caused to remove long-term-memory files at each restart, which is not desired.

• The previous root is now the default for short-term-memory
• Long-term-memory directory now follows the XDG Base Directory Specification.

[codecov]

Codecov Report

Attention: Patch coverage is 63.88889% with 13 lines in your changes are missing coverage. Please review.

Project coverage is 66.93%. Comparing base (d423934) to head (d32d23c).

Files	Patch %	Lines
karabo/util/file_handler.py	63.88%	13 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #564      +/-   ##
==========================================
+ Coverage   66.88%   66.93%   +0.04%     
==========================================
  Files          49       49              
  Lines        4980     4996      +16     
==========================================
+ Hits         3331     3344      +13     
- Misses       1649     1652       +3     

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[mpluess]

LGTM