Extend `createSettingsStore()` to allow multiple usage within a module.

## Feature Description

At the moment `createSettingsStore()` can only be used once within the scope of a module, due to its hardwired names e.g. `getSettings()`.

It would be useful to be able to provide an additional identifier to distinguish the generated Redux infrastructure, so as to allow `createSettingsStore()` to be used for other types of settings within a module e.g. user settings, additional site settings such as Consent Mode, etc. This would allow us to cut down on boilerplate Redux when introducing new non-module settings.

So, for example we could provide an identifier like `consentMode` and the resulting selector would be `getConsentModeSettings()`.

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## Acceptance criteria

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## Implementation Brief

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### Test Coverage

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## QA Brief

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## Changelog entry

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Start by locating createSettingsStore() and the existing getSettings() selector generation. Trace how the generated Redux infrastructure is named, then determine how an identifier such as consentMode should produce distinct selectors and avoid collisions. Done means multiple stores can coexist within one module, with tests covering the separate settings usages.

Written by the indexing model from the issue text.