Indexer: Improve perf by deferring index DB commit

[martin-kokos]

Since we're writing to a local sqlite, we're not worried about losing connection to a remote DB and losing consistency, so we can defer the commit until the end.

This speeds up indexing by about 30x.

[martin-kokos]

My editor removed some trailing whitespace too.

[ivbeg]

@martin-kokos thanks, I considered to replace sqlite with duckdb to speedup analytics after data processing.

[martin-kokos]

That's a separate topic, I think.