Empty State: Use name property on icon in empty state for custom icons

[RasmusKjeldgaard]

Which issue does this PR close?

This PR closes no issue, but fixes that the customName property was always set on icons in empty-state, giving a customName deprecation warning for icons even if a builtin icon name was used.

Additionally it deprecates the empty-state customIconName similarly to the icons customName.

Does this PR introduce a breaking change?

• [ ] Yes
• [x] No

Are there any additional context?

Checklist:

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