Emit log message when saving reproducers

[samalws-tob]

Fixes #1179
One problem with this: sometimes this message should be prefaced with a \n and sometimes it shouldn't. Example:

[2024-06-12 14:08:43.07] Saving corpus... Saving reproducer to asdf/coverage/9205690443874393131.txt
Done! (0.042806s)

Should be:

[2024-06-12 14:08:43.07] Saving corpus...
Saving reproducer to asdf/coverage/9205690443874393131.txt
Done! (0.042806s)

Any suggestions for how to do this in a consistent way are appreciated