`hierarchies`: Remove `@internal` tags from public APIs that aren't exported through the barrel

[grigasp]

Using a type guard to get @internal type from a @public one makes linter angry, e.g.:

const node: HierarchyNode = getNode();
if (HierarchyNode.isLabelGroupingNode(node)) {
  console.log(node.key.label);
}

gives:

[changeset-bot[bot]]

🦋 Changeset detected

Latest commit: 4952c0b2062cf3ef638af20917394742631a691e

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 2 packages

| Name | Type | | ------------------------------------- | ----- | | @itwin/presentation-hierarchies | Patch | | @itwin/presentation-hierarchies-react | Patch |

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[github-actions[bot]]

Hierarchies benchmark

Benchmark suite	Current: 4952c0b2062cf3ef638af20917394742631a691e	Previous: 6991bd34241ece8289c0916d3baed709ad3a783e	Deviation	Status
flat 50k elements list	4016.37 ms	4063.98 ms	-1.1715%	✅
flat 50k elements list (P95 of main thread blocks)	71 ms	74 ms	-4.0541%	✅
grouping by label	9862.96 ms	10047.77 ms	-1.8393%	✅
grouping by label (P95 of main thread blocks)	56 ms	63 ms	-11.1111%	✅
grouping by class	9969.41 ms	10158.2 ms	-1.8585%	✅
grouping by class (P95 of main thread blocks)	45 ms	47 ms	-4.2553%	✅
grouping by property	10526.63 ms	10735.81 ms	-1.9484%	✅
grouping by property (P95 of main thread blocks)	44 ms	80 ms	-45%	✅
grouping by base class (10 classes)	7184.94 ms	7392.17 ms	-2.8034%	✅
grouping by base class (10 classes) (P95 of main thread blocks)	75 ms	82 ms	-8.5366%	✅
grouping by multiple attributes	26621.45 ms	27189.94 ms	-2.0908%	✅
grouping by multiple attributes (P95 of main thread blocks)	56 ms	71 ms	-21.1268%	✅
hide if no children required to finalize root, w/o children	43396.87 ms	46325.78 ms	-6.3224%	✅
hide if no children required to finalize root, w/o children (P95 of main thread blocks)	37 ms	40 ms	-7.5000%	✅
hide if no children required to finalize root, w/ children	159.31 ms	174.04 ms	-8.4636%	✅
hide if no children required to finalize root, w/ children (P95 of main thread blocks)	0 ms	0 ms	NaN%	🚨
models tree initial (Baytown)	53.27 ms	55.76 ms	-4.4656%	✅
models tree initial (Baytown) (P95 of main thread blocks)	0 ms	0 ms	NaN%	🚨
models tree full (Baytown)	7499.43 ms	7559.08 ms	-0.7891%	✅
models tree full (Baytown) (P95 of main thread blocks)	90 ms	81 ms	11.1111%	🚨

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