Tagged components milestone 2: no more indicators

[teh-cmc]

The second milestone for tagged components is to remove the concept of indicator components entirely. The semantics of the viewer must not be impacted in any way by that change.

• Remove all codegen related to indicator components.
• Replace all logic that relies on querying for indicators with new descriptor-based logic ("is there anything on that path that belongs to the Points3D archetype?").

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• Part of https://github.com/rerun-io/rerun/issues/6889
• Requires #7948