[location] Update the location indicator to use layer persistence

[jmkiley]

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Fixes: < Link to related issues that will be fixed by this pull request, if they exist >

Pull request checklist:

• Briefly describe the changes in this PR.
• Include before/after visuals or gifs if this PR includes visual changes.
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Summary of changes

This PR:

• Updates the LocationStyleDelegate to use _addPersistentLayer(). This allows the user location puck to carry over to new styles. The default behavior of the LocationIndicatorLayer has not changed. It now uses layer persistence as opposed to watching for style changes.
• Removed the style change subscriber, which was a workaround for lack of layer persistence.

iOS equivalent to the location portion of mapbox/mapbox-maps-android#368

User impact (optional)

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[jmkiley]

Will update style gen for this change.