feat(firebase_ui_database): Allow reversing the database query

[Rexios80]

Description

Adds a reverseQuery option to FirebaseDatabaseQueryBuilder

Related Issues

N/A

Checklist

Before you create this PR confirm that it meets all requirements listed below by checking the relevant checkboxes ([x]).
This will ensure a smooth and quick review process. Updating the pubspec.yaml and changelogs is not required.

• I read the Contributor Guide and followed the process outlined there for submitting PRs.
• My PR includes unit or integration tests for all changed/updated/fixed behaviors (See Contributor Guide).
• All existing and new tests are passing.
• I updated/added relevant documentation (doc comments with ///).
• The analyzer (melos run analyze) does not report any problems on my PR.
• All unit tests pass (melos run test:unit:all doesn't fail).
• I read and followed the Flutter Style Guide.
• I signed the CLA.
• I am willing to follow-up on review comments in a timely manner.

Breaking Change

Does your PR require plugin users to manually update their apps to accommodate your change?

• Yes, this is a breaking change.
• No, this is not a breaking change.

[lesnitsky]

@Rexios80 could you please merge the latest main into your branch?

[lesnitsky]

@Rexios80 could you please resolve a conflict and merge the latest main again please?

[rrousselGit]

Hello!

Some tests would be great. Otherwise lgtm

[Rexios80]

There are no existing tests for the Database UI widgets. Since this is a small change, I believe adding those tests is outside the scope of this PR.

[rrousselGit]

Oh I saw that you did it for database. We'd want to do it for Firestore too.

[Rexios80]

Firestore queries have built-in support for reversal

[rrousselGit]

You're right, we could use orderBy/descending. LGTM then