Fix initial virtual chunks leaving ghost indices in some scenarios

[teh-cmc]

When initializing a virtual ChunkStore via ChunkStore::insert_rrd_manifest, it was possible (and even somewhat likely) to end up in scenarios where the original virtual chunks would keep declaring themselves as missing forever, leading to infinite spinners all over the place.

This was caused by an oversight on the write path, which didn't account for these ghost indexes. This PR fixes that.

That's the entire fix:

if matches!(
    self.direct_lineage(&chunk.id()),
    Some(&ChunkDirectLineage::ReferencedFrom(_))
) {
    // If we reach here, then a chunk that was previously virtually inserted using `insert_rrd_manifest`
    // is about to be physically inserted for real.
    //
    // We don't know what's gonna to happen to this chunk during its insertion: it might be
    // added as-is, or be compacted into another existing chunk, or immediately be split into
    // smaller chunks.
    // If the chunk doesn't get inserted as-is, for whatever reason, then it will leave behind
    // it the ghost indexes from its original virtual insertion, which will lead downstream
    // systems to believe that some chunk is missing, forever, even though it's not: it just has
    // been inserted under a different name.
    //
    // The fix is simple: always unconditionally clean up the indexes when a virtual chunk
    // gets physically inserted.
    all_diffs.extend(
        self.remove_chunks_deep(vec![chunk.clone()], None)
            .into_iter()
            .map(Into::into),
    );
}

• Closes https://linear.app/rerun/issue/RR-3740/loading-indicator-in-fully-loaded-recording

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Before:

After:

[github-actions]

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Result	Commit	Link	Manifest
✅	8759e4f	https://rerun.io/viewer/pr/12645	+nightly +main

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