Using a runtime with no lifo slot.

[fulmicoton]

As spotted by @PSeitz, the unstealable lifo-slot is causing the
doc processor and the indexer to run on the same thread.

For the moment this is disabled by default and only apply to the
indexer blocking runtime.

lifo slot disabled

➜  quickwit-dynajson cat ~/data/gharchive.json | ./quickwit index ingest --index gharchive4
❯ Ingesting documents from stdin.
⠏ [00:01:56] 1.43 GiB/1.43 GiB (5.7 MiB/s)                                     Ingested ✔ documents successfully.
➜  quickwit-dynajson
➜  quickwit-dynajson ./quickwit index create --index-config ./index.yaml

with lifo slot

➜  quickwit-dynajson cat ~/data/gharchive.json | ./quickwit index ingest --index gharchive4
❯ Ingesting documents from stdin.
⠇ [00:00:23] 459.65 MiB/459.65 MiB (17.1 MiB/s)
⠋ [00:00:23] 459.65 MiB/459.65 MiB (17.1 MiB/s)
⠏ [00:01:39] 1.43 GiB/1.43 GiB (5.7 MiB/s)                 Ingested ✔ documents successfully.