cleanup: flowd logs should be in their own directory

[jon-stumpf]

Important notices

Before you add a new report, we ask you kindly to acknowledge the following:

• I have read the contributing guide lines at https://github.com/opnsense/core/blob/master/CONTRIBUTING.md
• I am convinced that my issue is new after having checked both open and closed issues at https://github.com/opnsense/core/issues?q=is%3Aissue

Describe the issue

flowd logs are placed in /var/log. And, it appears that flowd maintains previous logs files with a six-digit suffix ".nnnnnn". This clutters /var/log which is undesirable.

Desired behavior

flowd log files should be placed in their own directory (e.g., /var/log/flowd) similar to how system log files that are placed in /var/log/system.

Environment

Software version used and hardware type if relevant, e.g.:

OPNsense 24.7.12-amd64