chore: make android icon res access runtime safe

[jaidensiu]

Summary

variant availability is currently a runtime concern on Android. every icon exposed all three variants as nullable res IDs (even for variants it doesn't ship) so a wrong variant compiled fine but failed at runtime

// AntennaSignal ships no solid variant, but the type system doesn't know that
// IllegalArgumentException at runtime
val resId = requireNotNull(NucleusIcon.AntennaSignal.solidRes)

variant availability is now encoded in the hierarchical type system where each icon implements HasOutline / HasRegular / HasSolid exactly for the variants it has, so res IDs are non-null and the same mistake no longer compiles

// compiler throws error since AntennaSignal has no solidRes variant
NucleusIcon.AntennaSignal.solidRes