Partially inspired by rfc5424, along with a few other idioms I picked up
along the way.  This should allow one to tweak the log level by setting
a minimum log level in the `Log' namespace.  Right now I've set the log
level to debug in the main entry point.

Users should be able to copy the logs from the infodialog box, along
with version information for slightly easier troubleshooting.

I'm leaving this commit here instead of squashing, so that in the
future, we could technically just reverse this commit.

This implements a very simple circular buffer that will take the last N
lines in a log file, and keep those instead.  Right now the maximum N is
hardcoded, but the code is written in a fashion that we can revisit some
of this, and add toggles where we see fit (for example in a settings
dialog or so).

I tested out the functionality this way:

        $ yes some-log-line | nl | head -5000 > log.txt

And then running PTE2 with a max log size of 1000, I noticed the logfile
like so:

        $ head -10 log.txt
        4001  some-log-line
        4002  some-log-line
        4003  some-log-line
        4004  some-log-line
        4005  some-log-line
        4006  some-log-line
        4007  some-log-line
        4008  some-log-line
        4009  some-log-line
        4010  some-log-line

and the bottom:

        $ tail -10 log.txt
        2023-12-30T14:38:32Z: [debug]: finding translations for locale:
        2023-12-30T14:38:32Z: [debug]:   locale: en-US
        2023-12-30T14:38:32Z: [debug]:   locale: en
        2023-12-30T14:38:32Z: [debug]:   locale: en-Latn-US
        2023-12-30T14:38:32Z: [debug]:   - checking: /home/psyomn/.local/share/powertab/powertabeditor/translations
        2023-12-30T14:38:32Z: [debug]:   - checking: /usr/local/share/powertab/powertabeditor/translations
        2023-12-30T14:38:32Z: [debug]:   - checking: /usr/share/powertab/powertabeditor/translations
        2023-12-30T14:38:32Z: [debug]:   - checking: /home/psyomn/programming/cc/fork/powertabeditor/build/bin/data/translations
        2023-12-30T14:38:32Z: [debug]:   - checking: /usr/share/qt/translations
        2023-12-30T14:38:32Z: [debug]: loaded qt base translations from /usr/share/qt/translations/qtbase_en.qm

and last checks:

        $ nl log.txt | head -1
             1    4001  some-log-line
        $ nl log.txt | tail -1
          1011  2023-12-30T14:38:32Z: [debug]: loaded qt base translations from /usr/share/qt/translations/qtbase_en.qm

This adds a custom format wrapper for QString objects, so that they can
be logged directly.