[UX] Show progress bars

Some progress dialogs can show very large numbers, which makes it difficult to estimate the progress at a quick glance. Examples include

- Full sync dialog

- Check Database

I propose replacing these progress dialogs with percentage-based ones.

Anki Desktop shows the progress with a progress bar, which is also clearer than raw numbers.

Related:
- https://github.com/ankidroid/Anki-Android/pull/18341

I remember David suggesting something similar before, but I couldn't find any issue.