gui text filter with Wildcard option doesn't work with multiple files loaded

[eneelo]

Describe the bug
GUI fails to list time series names when more than one file is loaded and filter option is set to "Wildcard".

To Reproduce
Steps to reproduce the behavior:

1. Install qats version 5.0.3.
2. Open GUI and load a single file. Verify that time series names are listed.
3. Load a second file and observe how all time series name disappear from list (keep filter option on "Wildcard").
4. Set filter option to "Regular expression" or "Fixed string", and see how time series names are listed again.

Expected behavior
Time series names should still be listed when second file is loaded.

Screenshots
Time series names listed as expected with "Wildcard" option:

After second file is loaded:

Cause
A likely cause is the backslash included in the name after second file is loaded. This backslash is not escaped, causing issues for the wildcard-based regular expression in the qt module (e.g., pyside6).

Suggested solution
Use forward slash (/) instead of backslash (\) as separator in full time series names.

Other comments
A related issue is #110, see the comment: #110 (comment)