Adopt recommended file save actions upon database mode change

[Ka0o0]

Hi,
As first discussed in #5565 currently save actions do not change if one switches from biblatex to bibtex or vice versa.
For a user it might be confusing if the recommended saving actions are not updated.

Ideally, when changing the database mode and the user has selected the recommended save actions, the save actions should be updated as well.
Recommended save actions were introduced in #2051.

[koppor]

We need to bring back the sensible defaults from #2051. I did not find the respective PR yet.