Support incremental ingest for SortedTemporalChunks

[0n41rd4]

Related

• Implements // TODO(emilk): handle incremental ingestion from 9a67723 ("Support progressive ingest of the rrd manifest")

What

RrdManifestIndex::append() is calling SortedTemporalChunks::new() with the
full concatenated manifest on every delta, rebuilding the sorted cache from scratch.

In this PR:

1. RrdManifestIndex::append() calls self.sorted_chunks.update() with just
   the delta manifest, not the full accumulation.

2. SortedTemporalChunks::update() tracks delta-introduced chunks in a local
   BTreeMap scratch map. Per-component merges extend existing sorted vecs
   with only the new entries. The bottom-up tree walk reads from the scratch map
   instead of rebuilding per_entity from all chunks.

---

A separate branch incremental-update/test-bench on this fork has a test and a timing benchmark I used during development:

Benchmark (2000 entities, 40 deltas, 4 components, release mode):

Approach	Time
Full rebuild (new() + extend/sort/dedup)	~2000ms
Incremental (this PR)	~490ms

[github-actions]

Hi! Thanks for opening this pull request.

Because this is your first time contributing to this repository, make sure you've read our Contributor Guide and Code of Conduct.

[0n41rd4]

hi, is this algorithm something you were interested in reviewing?