refactor: move some CollectionHelper methods to SetupStorage.kt

[david-allison]

Note

Assisted-by: Claude Fable 5

Purpose / Description

I split this out of the following PR for a quick review.

• feat: no longer implicitly set collection path when DB is used #21343

Prep for moving CollectionHelper to :anki-common.

Collection creation will become a startup concern, but collection
access will move to :anki-common.

Fixes

• Part of Consolidate validation in app entry points #19552
• Part of Don't force full (F-Droid/GitHub) releases users to grant the All files access permission #13574
• Part of Architecture Discussion: Module Extraction #20737

Approach

How does this change address the problem?

How Has This Been Tested?

Non-functional

Checklist

• You have a descriptive commit message with a short title (first line, max 50 chars).
• You have commented your code, particularly in hard-to-understand areas
• You have performed a self-review of your own code
• UI changes: include screenshots of all affected screens (in particular showing any new or changed strings)
• UI Changes: You have tested your change using the Google Accessibility Scanner

[criticalAY]

SetupStorage isn't self-contained yet, fine and expected for an incremental split from #21343 so all cool, thanks