[UX] Rename instances of "database update(s)" to "system update(s)"

[klonos]

We do CMI config file updates too, which are not db updates. Proper would be "Database and config updates", but too verbose. I think "system" encompasses both db and config, so I think that we should go with that unless there are better suggestions.

[klonos]

I can try a PR if we agree on the name.

[klonos]

This was recently brought up by @laryn in Zulip, during the preparation of the 1.22.0 release: https://backdrop.zulipchat.com/#narrow/stream/218635-Backdrop/topic/Release.20Day/near/282444669

Also, is this term "database updates" potentially a misnomer at this point?
e.g. an update hook that only affects CMI

...

I found an update hook here: #336
Which prompted the question above since it's a CMI update (not a database update) but will still trigger the red warning, right?

[indigoxela]

I'm supporting this! And if it were only that I don't have to 🙄 on every Backdrop update with CMI-only changes.

I'm not sure if I can help much with wording, though. ("System updates" seems a little weird to me.)

[klonos]

Here's an initial PR for this: backdrop/backdrop#4203

I have changed things to "system updates" for now, but happy to change it to anything better we may come up with.

I have left 3 instances of "database update" in cor/modules/system/system.api.php, since these were legitimately referring specifically to database schema updates.

[klonos]

Thanks for having a look @kiamlaluno 🙏🏼 ...any others to chime in? ...any thoughts re using "system updates" for what we should be calling these things? ...any other suggestions?

PS: I've rebased and pushed changes, which triggered the re-creation of the PR sandbox if anyone wants to poke around the UI.